For LH 2.2, the main 25 amp FI fuse is indeed under the hood in a flat fuse holder on the driver side (left) fender. This fuse holder can cause all kinds of grief. The fuse can easily corrode or overheat and make poor contact. Without it the system (radio suppression) relay will not get power and the injectors will not open. The result can be intermittent stalling/hesitation or a no start situation. The original fuse should be replaced with a marine-type water proof in-line fuse available from marine supply shops, auto parts distributors (like NAPA) and mail order from ipd. Solder the splice and use shrink wrap (or liquid electrical tape).

If jumpering the fuel injector relay contacts at the fuse panel allows a start then the relay has obviously failed again or is somehow not being triggered. Simply replacing the relay again won't cure the problem if the source lies elsewhere. From my original thought, a worn fuel pump may still deliver enough fuel, it may just be overworking to do it. However, when a fuel pump starts to seize in this manner I would expect signs of fuel starvation (hesitation) at higher revs. As you mention, a faulty FPR might be the culprit if it is overtaxing the fuel pump and by-passing too much fuel back to the tank. If the main fuel pump is very hot to the touch then one of these things is likely what's happening. Another possibility I'm wondering about is if the Hall Effect (rpm) sensor in the distributor is starting to act up. You may need a more professional analysis of your fuel system to determine what's going wrong by measuring fuel pressure at the fuel rail before and after the FPR at various revs and checking the control signal at the fuel pump relay.
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-Dave (not to be confused with a real expert, just goofing around at this)