I think you should keep trying, craft new weapons / equipment, upgrade them, equip good accessories on your team that have special abilities (IIRC they're listed inside [ ] brackets in the description), et cetera. It shouldn't be too hard if you get a good team going, as far as I remember if you got past the spiders, the snake shouldn't be too tough. This version's latest boss is going to be a real challenge again.
By the way, did you clear the sidequests? By doing them, you can save a girl and then go into her dreams for a bonus dungeon (added together with the jellyfish/snake area) with slightly different gameplay, a strong boss and some good rewards, iirc the recovery flower items.
Included my saves:
#1 is the whole content finished and boss defeated, though I couldn't understand what to do with the mouse in the treasure room (talk to some chicken maybe?). You can redo the turn-based half of the boss fight as often as you wish.
#2 is the save file I prepared before the 4.00 update, so if you just wanna skip the jellyfish/snake area, this should be perfect..