Take away Immunities

[Juas]

Hello, how is it going?

I want some help with taking away immunities from the game, please.
I am making 2 mods, one for playing with my friends on Lan with Hamachi, and another one (with bigger changes) for me, and I wanna lower resistances to max 75%. To me, playing alone, it gets very tedious, and, some times, impossible to continue with the game on Inferno.
I know you can, supposedly, lower them on monstats.txt, I did it a few times in the past, but I never had too much opportunities to test it right, and it doesn't work on unique/boss monsters, or even champions if I remember right.

Well, it would help me to know if monstats.txt actually do changes, and what else I need to do to accomplish this. Please, if you know the answer, respond me in a "step by step" way, I'll appreciate it.