I'd add religion too. Leif Eriksson was a Christian and the Christian element in Vinland (and no doubt ambitious Christian priests from elsewhere in the Norse world) would find it desireable to proselytise to the Amerindians of the region. I don't think we'd see large-scale conversions, but we'd certainly add a Christian influence into Amerindian religion that might spread very widely. Jesus might become associated with culture hero type figures common in Amerindian mythology.
a)I imagine more than 2 centuries to to expand beyond the Mississippi. Horses did not expand much faster in the Bronze Age.
Horses dispersed into the North American West in the early 17th century from New Mexico, and by the mid-18th century were revolutionising societies from the Canadian Prairies to the Columbia Plateau despite the disadvantages of the breeds the Spanish brought (namely their intolerance to cold). In the Andes, the Inca remnants owned and used horses. If there's anything that would spread fast, it's horses, although there is the issue that the Eastern Woodlands aren't as good for horses as the Plains and Plateau were. But still, I'd say maybe 150 years to get horses to the Mississippians and eastern edge of the Plains, then a rapid spread across the Plains and to the Puebloans in the next 50 years, then another 50 years to get horses to the Plateau and another 50 to the Pacific, California, and Aridoamerica.
Other animals would spread a bit slower I think. But sheep will be very useful for wool (the availability of winter clothing, often made from deer, played a role in limiting Amerindian populations in the Northeastern Woodlands OTL). Chickens are easy to raise so may be easy to spread very widely, adding additional protein. Pigs will likely go feral and thus mostly be important for ecological issues they cause plus the value of hunting wild boars. For goats, not sure, but probably decently useful. Cattle may be very useful if their role as oxen spreads, but this may be slow (the Norse aren't exactly just giving breeding stock away) and only just beginning to spread onto the Plains by the 16th century.
b)Would they really compete with local crops enough to instigate a rapid spread?
Maize farming was very recent in New England in 1000 and only poorly at best established in the Maritimes and the St. Lawrence in the 16th century so without a doubt. Same goes for the Great Lakes area, maize farming was marginal in this era and remained marginal. Barley, wheat, and rye are much better grains for the cooler climate than maize (a tropical/subtropical plant).
c)Even slower, I don't think it would go much beyond the Atlantic or Great Lake region if it's adopted, in Europe it took like 3-5 centuries for Iron to reach northern Europe from Greece and this involved larger distances and no bronze base.
Copper was an important trade item in Mississippian civilisation. In older times the Old Copper Complex existed but collapsed in part thanks to the depletion of easily malleable copper. Metalworking enables access to a much greater copper base. There is admittedly the need for skilled smiths, but for a Norse coppersmith there's a lot of money and fame to be made settling in a large Indian village. By this means copperworking could diffuse across the Plains, using copper deposits of the Canadian Shield and the Great Basin. I think by the 16th century we'd see vastly increased copper usage in Aridoamerica/Oasisamerica, possibly the Great Basin in general, likely in California, and in the Pacific Northwest, where native copper has a long history of usage and the locals were very knowledgeable about its usage. I believe we'd see centers of copper-working which are famed for it where the copper being produced is a sort of arsenical bronze. It's plausible, but a bit of a native wank, to see indigenous knowledge of tin bronze, although that might be a product of the Norse exchange. The best sources of tin are on the Canadian Shield, northwestern Nevada, northwestern Mexico (IIRC these deposits were known to indigenous cultures of northwestern Mexico), and the Kootenay region of British Columbia.
I think ironworking would be harder to spread beyond the Great Lakes and Mississippi, although would likely appear in the Southeast as well. The temperatures required are very high meaning there's a high fuel requirement. They'd obviously appreciate iron goods but find it easier to just import it from across the Plains.
d)Probably no real spread outside native societies directly under or in strong contact with the Vinlanders. They were not particularly literate themselves and to foster literacy you generally require more urbanization and advanced state formation and the Vinlanders wouldn't bring with them the kind of attitude Christian Iberians had in the 16th century, with their priests translating texts, writing native languages down etc.
This was the dawn of the Mississippian era, there's plenty of things the priest-kings and rulers of those cities might want to write down. OTL the Ojibwe had some writing for their secret societies and the Cree, Blackfoot, and some Athabaskan groups adopted syllabics brought by missionaries. In some cases the syllabics spread so fast that many groups assumed it was a native invention. They just need to be introduced to the concept of writing. As an Old World example, look at the spread of Phoenician writing.
A problem is the hugely divergent nature of Amerindian languages compared to Norse. Siouan languages and Muskogean languages (spoken by many Mississippian groups, the former likely including the people of Cahokia) aren't challenging to adapt to Latin (or god forbid even Runic), but other languages associated with the Mississippians like Natchez or Yuchi would be rather difficult. So you'd need enough Norse traders there and local traders, priests, and others receptive to the idea of writing and willing to take the time to adapt the Norse script to their languages.
From the Mississippians it would spread across the Plains and spread southwest to Aridoamerica and Mesoamerica (possibly, they had their own useful semasiographic writing). The Puebloans are complex enough to have plenty of uses, while in California you might have an Ojibwe-esque case where widespread religious societies like Kuksu, Hesi, and Chingichngish/Quaoar adopt it for ritual purposes. The Pacific Northwest has both the secret societies and population density to make plenty of use of writing.
The big one is sails. OTL Pacific Northwest Indians adopted sails in imitation of European ships. Still, Norse ship construction might be seen as more efficient than typical Indian canoes so we could easily see imitations and copies throughout the Mississippi Basin and the Gulf although I don't think they'd be able to transmit shipbuilding tech past the Rockies. This could actually be huge since sailing and sturdy Norse ships make the Gulf of Mexico much easier to navigate meaning we could have some serious contact between the Mississippians and Mesoamericans like the Huastec and especially the Maya, plus Caribbean groups like the Taino.
Norse shipbuilding and sailing would likely appear in the Pacific at some point, transmitted by the Maya or nearby groups, and slowly spread up and down the Pacific coast. We could expect to see the Manteños of Ecuador (in limited contact with Pacific Mesoamerica) adopt it and also the peoples of Aztatlan at the northwestern fringe of Mesoamerica. From there it's more difficult to spread since Baja California is such an obstacle and the Yumans of the Colorado River don't really need it (except to trade with Aztatlan of course). But perhaps the Chumash (perhaps California's strongest seafarers OTL) would get a hold of sailing and they'd allow some expansion of sailing north. I think we'd have this "indigenous" (Norse-facilitated) expansion of sailing meeting later European sailing traditions in the Pacific Northwest, although since the Salish would encounter it at the same time the Haida and Wakashan groups would the Salish would do a lot better in the wars of the 18th/early 19th century brought by Europeans in the Pacific Northwest.
Highly doubtful. Amerindian architecture in the Northeastern Woodlands was perfectly functional and had no need to borrow from the Icelandic tradition of which Vinland would stem from. I'd consider the stave church perhaps the greatest architectural achievement of medieval Scandinavia, more distinctive than the post churches commonly found in this era. OTL Iceland didn't have any stave churches (historically) so it's highly doubtful such a tradition would be introduced into the New World. Although it's possible a Vinlandic clergyman might pave the way for such an introduction by his personal links to mainland Norway. But even if we have a stave church in Vinland, I highly doubt we'd see similar borrowings in Amerindian civilisation.