You might pull the yellow "ign" wire off of the starter relay on the inner fender to termporarily disable the starter just for these tests. Take off any and all wires from the coil negative primary terminal and with the ign sw on (ign1) w a jumper wire ground this coil male neg pri terminal to ground repeatedly like Morse Code & see if the dist to coil secondary wire held 1/4" from the valve cover sparks then have a helper turn the ign sw to "start" (ign2) & hold it there & you repeat & see if it sparks. If it sparks on one or both tests then the ECU and the coil are good (though they both have been known to act up when hot). If not one of them is bad and or they are not getting fire (either in "run" or "start" and I would make sure the ECU is cleaned/scraped on the bottom by one of the mounting bolts even though it is unpainted just to be sure). If you have a spare dist plug it in & spin it by hand w the ign sw "on" and "start" & see if it triggers a spark from the coil secondary wire 1/4" from ground. The "point" of the ECU pentastar connector must get fire in "on" and in "start". Check the reluctor gap on your current dist & maybe reduce it to .005" at the tightest point which will be somewhere in the travel range of the vac adv (got a vac pump/Mityvac handy?). But with almost everything being new I'd think as you surmised a part time open but do check the reluctor gap.