Try exporting an animation too then open it in the same project with the mesh. Been a long time, but if I recall correctly that might fix the model's weirdness.
Also you could just using milkshape 3d to export the model into a format 3Dmax is more compatible. I suggest you try that as it might...
Or make something like the dark sword use more mana.
Or make make the big axes hit more than one enemy horizontally.
Or go back and make weapons use different amounts of stamina for normal attacks+special attack.
IM not too fond on weaponstat rolls either, tough prefixed weapons with sockets to put some stuff is okay.
However im with the idea that health shouldnt be able to raise as you level up, instead be affected by skills or race class. Same with defense being dependant only by the armor.
I do agree on what tothie says, because thats the only way for a game with rpg element where you have actual control over your character.
I dont know how to explain it but a way to understand it is to look at games like monster hunter (or dark souls maybe): characters dont level up but you get...
I think unity maps are comprised of models with the exception of the terrain.
What you could do it try to find on google for a method to convert HL maps into model files, and I believe theres some answer out there.
Or just get a modeller to recreate the maps while using the old ones as reference.
Just have someone who can make some concept art while guiding him/her to make sketches matching your preferred style for the game, or just make some drawings yourself if you feel confident.
Seriously people, nobody is going to make anything like you want to unless you tell/show them them...