The final skeleton room is very strong, but it is possible. I was running out of time by the end of the jam and didn't have time to balance it properly.
As for strategy, many of my strongest runs come from finding a lucky fish in shop 1 or 2 and coin pouch soon after. Coin pouch drops 1300 coins if you have lucky fish, this lets you buy almost any item you want for the rest of the run.
Hot pepper and razor wing are also very valuable if you can find them early. You can easily end up dealing 60+ damage per attack by the end of the run.
Thanks for playing the game! I don't intend on making any big updates to this prototype but I might add a few levels, items, and enemies, as well as do some proper balancing. This game seems to be doing well on itch so eventually it might even get a full release! Thanks again for playing.