Rescue situation, newer keeper

[Homebody]

Second: I would be inclined unless it would be detrimental to load some vitamins in his food proactively. If it’s water soluble and he gets rid of what he doesn’t need, that is. Is there a recommendation on brand?

I wouldn't treat with with vitamin supplements without a vet's approval. Snakes usually get all the vitamins they need from their prey. Adding vitamins without direction might cause other problems.