It could be anything. Check the spark plug terminals are screwed on tightly. It sometimes helps to turn the ignition on, let the pump run until cut off, turn off. Repeat this a couple of times before starting to crank the engine. It sounds like the battery is good though, managing all that cranking 😁.
The fuel pressure should be 58psi at the test point at the RH injector, if not then the pump is on it's way out usually. As Chris says, change it for a Walbro one if not already done as it will fail at the most difficult time otherwise.
