How did you disable it?
Pause or Stop Provider, Terminate from the on-access screen should do it.
The figure for memory usage seems high and may be down to the type of memory monitored and the program monitoring it. My own use whilst on-line (using the VM Size, which is a more accurate indication of actual memory in use), is much less, see image.
To permanently remove it (which I wouldn't recommend, lowers protection greatly, but that is your choice), using add remove programs, select avast anti-virus and click remove/change; from the next window select the change, you can now un-tick the elements you don't require.
I would suggest that there are better ways to save system resources rather than reduce your protection.