I'm a 2nd year at sussex, and do biomedicine. I can promise you - clubbing in brighton is so safe. SO SAFE.
I go out a lot, and i've never had any problems. I've seen hardly any fights, even at the end of the night. You just dont see it.
What you have to remember is that a Friday night in Btown is not representative of the normal student experience. Normally students go out between Mon - Thurs. Fridays you get less students and more adults / teens who have jobs and I can tell you, I dont go out on fridays because its noticeably rougher and you get a LOAD more weirdos.
Clubbing on mon - thurs there are LOADS of club nights, you went to 3. I love coalition, and pryzm - but I avoid shoosh like the plague. Its chavvy as hell and you get dreadful people in there. The only night I go pryzm is wednesday which is the student night, and its a GREAT vibe. Everyone in there is out to have fun, and I ALWAYS feel safe. Theres not been on time i've walked home (alone) and not felt safe. Please, PLEASE dont worry about the safety of clubbing in brighton. Its probably one of the safest towns about, because as we have two uni's in brighton everyone you see is generally a student, and theres a bit more of a community spirit.
As for drugs - this is the only thing in brighton which is a negative. Drugs are absolutely everywhere. The smell of weed is common in brighton, and to see people doing coke in a toilet isn't unheard of. (I've known people who have done it..) But unlike in london, the druggies here stick to themselves. You're not going to get shanked in a dark alley by a scary dealer.
Im repeating myself, but as I said I go out 3 ish times a week, and have never felt unsafe. There are creeps in clubs who try to grope you or get a bit close, but you get that everywhere. Friday night isn't representative. Shoosh is for chavs, and pryzm on fridays is full of weirdos. Coalition is good on fridays, and i've not been in there when it isn't absolutely popping, so you probably didn't give it a chance if you went to three clubs in one night.
I've waffled a lot here, but i cannot stress enough - I have categorically never had any issues in brighton when clubbing, and do not know anyone who has. The only downside is that drugs are common, and certain clubs have issues with mandy. (MDMA) But if you look past that, Brighton has the best club / night life in the south. You can't go wrong, I promise you. Brighton is safe, dont let that be an issue in coming here.
Any other specific questions, drop me a message.