GN

Grammar Nazis, get in here.
Which is most proper? :
"(it) assisted me in passing the exam"
"(it) assisted me to pass the exam"
"(it) assisted me with passing the exam"
or other?

Also, should it be
"assignments at university level"
or "assignments at a university level"

And can I end a sentence with "that I look forward to"

"With passing the exam"

and I believe it should "a university level"

Definitely the first in both if you want to sound proper. "assist me to pass the exam" is wrong, but "assisted me with passing the exam" is fine in colloquial situations. However, I'd change "assisted" to "helped" since it sounds more casual, but that's a matter of word choice rather than grammar.

"a/the university university level" sounds much better to me than the same phrase without the article. I can't think of any situation offhand where "assignments at university level" sounds better. If you want to just say "assignments at university", that's fine, but if you're talking about "university level" instead, include the article.

I'm not sure about your last question. You can say "I look forward to ~", but I can't think of any way you can end a sentence with it. If you inverted it, it might work; e.g., "Now THAT is something I look forward to."

Assisted me in passing the exam or assisted me with passing the exam are both acceptable. Most students would say something like "It helped me to pass the exam" though. Like the other guy said it's more of a word choice issue rather than a grammar issue at this point.

Use an article for the second question. Probably "the" would work best: "assignments at the university level." You could also say something like, "a university level assignment."

You can start a sentence like that, "I am looking forward to the weekend." "I look forward to seeing you at the party." Etc. Ending a sentence like that is not common and sounds awkward.

A lot of English comes down to word choice as grammar can be lax in some cases

If your question is about grammar (and not what "sounds right", because we'll be here all fucking day), it is totally acceptable, and has been for about 300 years, grammatically, to end a sentence with a preposition, as in "Going to the circus each year is an activity I look forward to" or something like that.