Alright, I think I finally found the issue.
It's somewhat anti climatic after all the leads I've chased down, and can probably be attributed to my own ignorance or inexperience.
But after checking the fuel filter, I went to replace it with a new one. I was feeling around the wiring casing on the fuel pump wiring and felt a rough spot/ snag. Turns out, the wiring had rubbed against something and was almost rubbed completely through.
I fixed it, installed the filter and haven't had the problem since. I had previously checked the wiring, but hadn't felt the top of the casing, and this was out of sight.
Anyways, hopefully this thread can die now. I really, really appreciate all the help and advice.