Raspberries lack physical AES instructions, I am not exaggerating when I say this could take 5-6 weeks to sync. There are other SBCs like the Rockpro 64 that would be way better suited for a node but the most economical option is getting used mini-pcs from ebay for $50.
It will have high RAM usage because it is constantly writing and reading during sync.
Yes! That is possible, check out this guide. Pruned db is smaller but it will first do a full sync and then prune it so you still need enough storage for the “peak”.