without cheats there are always options:
-you can get stagbreaker and try to destroy the spawner with it's aoe. since it hits through everything it may help.
-you can get your previous set of armor(which you should probably have, cuz swamp is usually a 3rd biome) and fight in it. with good food you'll be able to get your items back
-you can use corpserun buff: put 1 stone in your inventory and die at the entrance to the crypt (you can use monsters or type /killme command in the chat. it's not a cheat and it's available to everyone by default). then run back. take a corpse. immediately eat 3 food and while the buff will last you'll be nearly invincible(75%damage reduction and 10hp regen per second) which should be enough to retrieve your original corpse.

and it's false that you've wasted 50 hourse. at most you need to craft a new pick.

ps: btw you can build a bed and\or a portal on the crypt. which will make it a safe spot to respawn or run back faster.