On the nuts and fruits question, the situation may not be as sunny as it might first appear. Scurvy was one of the first problems I thought about when pondering the scenario, actually. Some Cretaceous fruiting plants that would have occupied North America and are still either around or have closely related descendants include
A. gigantea
P. nigrum
C. occidentalis
Magnolia spp.
W. nobilis
M.glyptostroboides
G. biloba
One thing almost all of these plants have in common is that their raw fruits or nuts are
not edible to humans without extensive processing that would be hard to arrange in a primeval context. Magnolias have edible (and tasty) blossoms, but only bloom two months out of the year and were probably never common sights. So that leaves really just the black pepper and maybe a few biloba berries to eat before you get sick off them.
There were probably plenty of other theoretically edible fruits, berries, roots, and nuts, but if you aren't dealing with plants you recognize, determining toxicity is a difficult, time-consuming, and dangerous game.
In this situation, I think I would be taking a risk and trying to go for fish. There's some
dangerous competition for them in the Cretaceous, but I have a hard time seeing how certain nutrients could otherwise be got reliably, especially out of season. Beetles would also be an option, and as primary pollinators, were pretty abundant during this time period and often contain the same vital plant nutrients. But they are also frequently toxic in the modern world, so you'd have to be nearly as careful with unknown insect species as with the plants themselves.
