find the cranking cell on your a/f table, timing table, and ve table. these values will tell you prob why it won't start.
my v/e table was way off on cranking and i had to drop it to .431 and .426. would foul the plugs real easy. my engine is about the same size as yours so this might work. my cranking cells are 200 rpm, .26 and -.56 on the map values.
if your plugs are fouling the time it took you to remove the dist. and retime your plugs could have allowed the plugs to dry.
if you floor the accel pedal it should turn the injectors off when you crank the engine by the way, if your plugs are fouling.
on the dual sync dist., you phased the cam light, dist light, and rotor?
i don't know if your fuel return setup would fool the dfi, but you should be able to run a vacuum hose from the throttle body to the regulator. the fuel pressure will then be adjusted by manifold vacuum and read lower by about 5 lbs, but this is correct. and switch to return on the dfi. if i remember correctly, the fuel pressure is set without engine running.
did you force the timing to check if the crank was matched with what the dfi was using? if these are different then you will have to use crankoffset to match the numbers.
don't worry, i went through the same thing you are. you're going to learn a lot.
you're not getting any trouble codes?