I just saw your post for the first time and thought I might have something to add. I teach at a university here in a Canada and have faced many of the same problems you have. Though the school I teach at has never handcuffed me so far as to tell me I am not allowed to spar in my classes and I might be inclined to walk away from any institution that wanted me to teach fighting without allowing people to spar in a controlled environment. That's like teaching your someone to drive by showing them how and then sending them to drive around the block by themselves.
Firstly Hope had some very good ideas as to how to help students. When I am doing warmup/drills I move around the room providing input to individuals to help them improve their technique but I am always sure to spend time with the more advanced students as well. This prevents the newer students from feeling singled out and the older students from feeling left out. If in moving around the class I find myself giving the same advice to 2 or 3 people that usually indicates that my initial description lacked something and I take that opportunity to stop the whole class and explain that point better.
Another thing I have done is that even though our class is blocked out for a two hour period I run the "official" class for only an hour and a half. Since you are teaching at a uni you will find that there are students who need to leave to study or catch a bus etc so people who need to leave after this time can. I encourage all students to stay though as I use that last thirty minutes for question period. This is the time when people can ask me additional questions about things which were not clear enough during class, or some of the inevitable "what ifs" that always come with drills, or even ask about things we haven't done in a while which they want to work on. I can also use this time to seek out any students for which I had additional feedback and provide it to them then in a situation where they don't feel like they are getting public criticism.
I have found that this works fairly well for me as the students who really need or really want additional attention remain behind and those who are less inclined or really need to go do not feel stuck there.
I hope this helps.