What should the pressure of the filter be at normal circulation.
Depends on your pool. Most systems run in the range of 10-22psi

What is normal maintenance for this type of filter.
Usually nothing except an occasional backwash.

Can I run this type of filter 24/7 to clear up cloudy water????
You can run it 24/7 but it probably won't clear your pool....You've probably got some chemistry issues causing the cloudiness. To keep us all from just guessing, post a complete set of test results for:
FC
CC
pH
Alk
CYA

With those results, you'll get lot's of solid advice on clearing your pool.