WingedKagouti: The highest + you can get in AD&D is +5 for armor, +5 for Swords and +3 for other weapons. With some special weapons having situational modifiers.
So, unless they break too far away from the basic rules, that should give you a decent guideline.
Sarisio: That's the point that max "+" differs from game to game. I think there are some +^ weapons in AD&D also (Carsomyr? My memory might be wrong on that one).
dtgreene: 9th floor is easy. Spirit Nagas and some other scorpion-like enemy, neither of which does anything nasty.
Sarisio: Difficulty curve in this game is very uneven. And it isn't exactly suited for lonely melee fighting style.
Thing is, there are two types of enemies.
1. Enemies who are non-threats, with the only danger being hit point damage.
2. Enemies that do nasty things that can require you to reload.\
When both common enemies are type 1, the floor is really easy to clear. Put a type 2 enemy in the floor and suddenly things become much more dangerous. Two type 2 enemies on the same floor can mean a lot of saving and possibly reloading.
IMO, the game should have had an option to prevent enemies with instant death attacks from appearing. That would make Death Real runs (for those inclined to do such things) more reasonable. As it is, one failed saving throw can end your game suddenly.