Well, if you pause the game and just look at one of your hits, you should see how damage is inflicted and how much is resisted, then you can work out what they're resistant to (and how much). So, if you're using something electrical damage and see that you're hitting but not doing much damage, then you should probably switch or cast a spell that weakens their resistances.
You should be very close to the end of the game now, maybe a couple of floors away.
*sigh* Looks like there's not much time left for me to give advice on your game then.
