I never had a problem not using cheats when playing the game. I even deliberately did not use some available features (like charms, except for one) or exploits (Frost on a weapon, scorpions, shadow potion + warrior's spin attack) to keep the game from getting too easy.
Resistances are not in percentage, though up around 100 or so does make you fairly immune.
A bow and hit-and-run tactics (also called kiting) is a widespread method in games for killing enemies much more powerful than yourself, and there are various methods to reduce this (faster enemy healing, better AI...). You can use this technique to kill Jake in Aleroth twice at the start of the game (the first time would bring you from level 1 to level 3, the second time to level 4).
