I'm not sure what El Shrimpo's resistances are, but in general, mages should max Know Creature (survivor skill, path of lore) to get that information and be able to choose the best spell for the opponent they are facing.
Hell Spikes do physical damage, so can not be resisted.
Save the game and learn one level of Burning Wall (if the lightning damage is not effective you can reload). By casting the spell and running around him in a tight circle, you can hold him in place for a few seconds, while he takes multiple hits off whatever sides he is touching. Even if you just run away from him (perhaps in a zig zag pattern), he should get caught up in the wall chasing after you.
Once held by Burning Wall, you could switch to Meteorstrike and left click as fast as you can, as long as your mana holds out.
Enough
restoration potions can get you through any fight. You could try switching to a melee weapon, or use hit and run tactics with a bow.