Illusion failure at low levels

I'm trying to play a character that is much different in that I will wear no armor and cannot use a bow or weapon, or destruction and conjuration schools of magic, to protect myself unless the game won't let me advance without it. But I'm having a hard time with illusion.

My main plan is to sneak and frenzy an enemy to start them fighting, fear off any extra mobs to try and protect the frenzied mob. And then calm the mob and just run by once the room is sufficiently clear. I'm also using alchemy to create potions like invisibility.

The problem comes in that an enemies resistance to illusion seems incredibly random, for example it seems most skeleton type monsters can't be frenzied... but rarely I can. Some "bosses" can be calmed some can't. I've even cheated and maxed illusion and certain mobs have just 100% resist or something even in the first few levels.

I'm also having trouble with leveling too fast, which makes the enemies resistance even greater. For example I get to level 10 very quickly casting just muffle, frenzy, calm, and turn undead. It seems like each cast is almost a quarter of a level of xp even on master difficulty. This leads to the issue of a spell working on anyone under lvl 8, but I level so fast that all the mobs in the next dungeon are above level 8.

I realize I'm playing differently than the game intends, but any suggestions on how to deal with this? I also level up faster than I get skill points to get high enough in illusion to unlock the higher level perks like animage or the human version. I haven't started the main quest yet, but I think the skeleton when you first learn FusRohDah will be a bitch on master with no weapons. I'm wondering if I can just run from him back into the dungeon and lead him to the swinging door in all the kill lydia videos.