1997 Chevy Astro fuel system trouble shooting

I have 97 Astro van that stops running every couple days and now won't start at all! Lets start from the beginning 4 weeks ago van stopped stranding the wife in the next town over she calls me up and I run over only to have it start right up. we had noticed the fuel pump whining loudly couple days earlier so I think easiest thing first right? fuel filter van starts up runs well fixed right? ..wrong! week later pump gives up. can't hear any thing from tank. when key is on. OK I kinda figured. so I install new pump. started up runs fine. fixed right? wrong! month later same thing quits but will re start in about 20 minuets. long story short I get out all my tools and my trusty CHILTONS book and start testing. oil pressure sensor test bad (engine dies when relay is pulled) so I replace it. Still dies days later. Fuel pressures low 44 psi. So I do the test (blocking return line) pressure goes way up. Fuel pressure regulator so I replace it (not a easy task on an astro van) I think I got it now real good pressure 68 psi. Runs great! better that it had is years. So I decide while I have the doghouse off I am going to clean it up I spray the entire engine compartment down with oven cleaner and scrub it down this works great washed with the hose now wont start. No worry's I think. "caps wet" let it set for an hour or so hour starts right up drives great. Fixed Right? Wrong! Dies in the road hour later will not fire at all except to backfire through the air filter. Like it out of time.so I think shorted something out .....so.. cap, rotor, coil , distributor, plugs, crank sensor, cam sensor still no start got spark nice and blue from coil not so much from plug and about out of money and patients PLEASE IMPART YOUR WISDOM ON ME.
THANKS SO MUCH. I FEEL BETTER ALREADY.
Bert.
San Diego Ca