My van has been stalling on 45+ minute drives.

This is a serious problem for me as I'm disabled and getting stuck far away is pretty rough. Not to mention, I don't know cars at all. Getting to the point: Usually on highway drives (or any of length) the vehicle is running just fine and out of nowhere it starts choking and stalling and finally dies. It DOES NOT lose power until pulled to the side and parked unless pushed. Temporary solutions are just letting it sit for extended periods of time. The mechanic I take it to tells me he can't "make it happen" but I've been stranded 3 times. After much internet research I've read there are many others with this problem and I see mostly solutions involving various sensors. Possibly, fuel being not delivered meanwhile air leaking in due to pressure on pedal and thus it dying. I'm assuming the basics have been covered by my mechanic so the question is now; does anybody have a more definitive idea or extra insight? You'll literally change a broke, 25 year-old, disabled guy's life.