Had some long overdue time off last week so I got back to this a bit. I decided to push the MAME config aside for the time being and get back to the boardset.
With a little guidance from a friend I managed to get the likely problem narrowed down. Did some reflow work and got the voltages back to proper ranges on all boards. Still no test flashes and garbage on the screen. Was advised to pull power from everything except the ZPU and a good ZPU alone should get the first three test flashes. Still nothing. Then was advised that the typical battery acid fallout zone is the z80's reset circuit. It did have some damage, not a ton, but whoever had it before me that took out the battery did leave some there. Cleaned up the rest of that, scraped off some residue, spent a lot of time with alcohol and Q tips, reflowing/cleaning, and still no change. At this point I was advised to check the reset pin on the z80 - which should be persistently high (around 4.5-5v). It's near zero so there is the problem. Next up is to trace the reset circuit back and find the problem, either an acid tweaked component or a bad trace. I don't see any likely bad traces so my guess is a pad that still needs to be redone or a dead transistor.
Of course, part of the way in, my old Weller station developed a major fault. I pulled the iron from the stand and it was glowing red from the tip to halfway down the iron shaft. My backup station is a 20/40 watt $20 model... 20 watts isn't hot enough and 40 is too close to trace lifting. So I need to pick up a new station when some money frees up.