With your tips I managed to complete the whole demo, I absolutely love it! It's awesome! I even killed the doppelganger.
Some random feedback/things I noticed, in no particular order. I assume you've looked into/fixed most of these already as the demo is pretty old, but anyway:
1) You can't actually drink the potions of Cure Paralysis in the snake room. Since you're paralyzed. Heh.
2) The second level of Dark Sorcerer's Tomb seems to lack one iron key, that may be intentional though (I took the goblin gang).
3) I wish movement could be slightly faster/snappier. When moving about the forest for example it would be nice to simply move with the keys super fast like in EOB.
4) When the goblins shoot with bows, there's a strange delay where it seems you can act, but have to wait until damage is over.
5) It's really weird that clerics can start with fire magic/firebolt when they can't learn it in-game.
6) Related to 5), the random stat spread of the "premade" characters is too wild. A starting wizard can have 13 or 20 spells...
7) It would be very nice to get some more information on combat stats. Freezing Spikes seemed to be the by far best spell. I'd love to see rolls, hit numbers, damage ranges etc. Maybe a combat log?
8) Related to 7), Level ups seem to do very little, only increase HP?