Thanks for such full reply! Yup, it makes total sense to not spend attack early (and defence too if you have more then current crab attack).
I'll gather my lucky totems and try it tomorrow, haha
UPD: The mighty crab has fallen! My main strategy was to 1) survive a first few rounds 2) use temp shields from the store as defence Because 10 shields cost 9 coins, and you gain +2 coins every round, you can indefinitely mitigate crab's +2 damage, while having profits from gold dice for yourself.