89 300e w124 major fuel problems

How could it possibly leak if you used new crush washers? Overtightening will cause leaking as it deformed the surface... Are you positive you did install all the washers? Fuel pump connection has two crush washers per bolt... same for filter too on eash side. There is no surface where the bolt or any component is without a washer in between.

Yes I am sure I replaced all of the crush washers. I also know they were not overtightened because I only used a wrench and my hands to hold the assembly. I doubt I could have possibly applied that much force to it that way. Also, when I first try to start the car it does not leak, but then as pressure builds up and more and more connections start leaking faster and faster the more I try to start it.

Fuel pressure regulator opens at a certain pressure thereby limiting (keeping constant) the fuel pressure. I don't remember the value for the 103 engine, but I belive it is some 4 bars.

If fuel pressure regulator is stuck, the pressure will keep building up until the internal overpressure valves of the fuel pumps open. And that is at 6 bars+ each, 12 bars+ in total.

I think you should look there. That also explains why your fuel pump blew in the first place.

And incorrect fuel pressure will cause incorrect fuel mixture explaning the no start.

I agree... I think you need to check the pressure... otherwise, replace the pressure regulator.