It´s something I have to deal with too. After some time the preview stops and the program WILL break down in a few seconds.
My advice:
-deactivate every filter in your avs. There should be just resizing and crop for working activated (oh you already did)
-Set the avs Premiere GUI to 2MB Max. Memory per avs script
-Deactivate Antispyware, Antivir scanners and firewall.
Optional:
Get something that displays your amount of memory on the right down edges in Windows (you know... the place with the icons). For example the Memory Optimizer of
TuneUp. Than work... And when you see that your program is going to shut down, look at the memory optimizer in the corner and remeber the state!
When you work and see the memory comeing next to the state, save your project, shut down Premiere and relaunch Premiere again.
I do it when I work in Premiere, this method works out fine.
After working and with all activated filters for export:
-Export only in uncompressed RGB and only parts (like very 30 seconds or every minute)