1990 Citroen Saxo Squeaking and stalling

Engine Performance problem
1990 Citroen Saxo Manual

Hi

I have abit of a habit of letting my car run on the red often.
Recently, the past few days, when i'm driving it jolts everytime i change gear and normally when i pull away in first (especially on a hill) it stalls. I can start it again easily but im back in the same boat within a couple of seconds.

I've been told it may be because running on the red sucks up all the dirt and crap and now my pipes may be blocked so the petrol cant flow freely, does this sound accurate?

Also when i have my foot on the accelorator it makes a horrible squeaking noise (although not all the time) and my partners dad said that could be my fan belt?

Please advise.

Many thanks