No engine spark, no start

I have the truck listed above K1500. I drove it home from work about a week ago, it was fine. Got home, went inside, came back out and it wouldn't start. Gave a really slow crank. I took the battery and had it tested. Tested good, and charged which I expected, it's pretty much brand new. So, I put it back in the truck, and tried again, and it slow cranked, but then after a hard time it started up. I let it run for a bit, shut it down, and it wouldn't start again. This time I pulled the starter, it wasn't bad but had some oil present inside, so I had it tested, it tested good, but I replaced it anyways because of the gunk. Put the new starter in, and tried again, this time it really didn't want to start, but after about five minutes of trying, it fired, but when I shut it off it wouldn't fire again. I charge and drop tested with a voltmeter, everything is in range. I spark tested with an Inline Spark Tester, the coil produced spark, but it never leaves the cap to the block. So I replaced my entire distributor system, and the coil, and the control module, the spark plugs, and the wires. Then tried again, same deal; no start, however she did gasp, like a weird backfire with no combustion. I'm now stumped.