ECU throwing a lot of codes but all sensors look good

I did a VG33ET swap on an '84AT and everything is installed, but I'm having issues getting this thing to run.

Usually it will fire right up and immediately die (within 1-2 seconds). Sometimes it'll take 20 seconds to start, then stumble, rev up in the 1400's, stumble in the 500's, up to 1400's, die.

One time it started running and it idled high, but nicely (seemed normal for a cold start).

Anyways, I got frustrated and pulled apart the ECU, found some burn marks so I ordered a new (used) one. Its supposedly the same model, though the circuit boards are clearly different

Anyways, now I'm getting error codes: 11,12,13,14,24,31,41

I've troubleshooted each of these and here are my conclusions:
11. Crank Angle Sensor. I did all the resistance tests on xenonz and it passed. I'm confident TDC is set correctly and on the intake stroke
12. MAF. I tried reading resistances here and they're pretty off but I was also struggling (borrowing a 30+ year old multimeter, mine is trapped in another state)… but IMO this should cause it to run bad, not stop after starting. And unplugging it doesn't change anything. Also, just from a visual inspection, the MAF looks perfect.
13. CHTS. Passed resistance checks and the sensor and harness are brand new
14. It looks fine to me and the dash reads 0mph even once it initially starts, couldn't find resistance checks. I heard I can cut some purple wire or something and that might help in case it thinks it's going too fast
24. Neutral Safety Switch. I don't really get what this means, it's turning over so I don't think that's the issue. Should I try jumping this?
31. A/C. I took it out.
41. Fuel Temp Sensor. Brand new fuel pressure regulator w/ sensor, and the wire was a little damaged but I put some dielectric grease on that

Any ideas? Worried the ECU I got is also bad… I don't really know how to test these. I tried unplugging all fuel-related sensors (CHTS, fuel temp, MAF, O2, TPS) and it didn't start at all, though that also could be due to the higher displacement and default programming not quite sufficient?

Running a Walbro pump and from what I can tell it's OK. Going to check fuel pressure tomorrow but I had someone squeezing the hose while starting it and pressure stayed consistent. I can't find any significant vacuum leaks, though there's a hole I just have covered with electrical tape where the right side PCV used to attach to the intake hose just after MAF (using a filter on the cover right now). Still I don't think that would do it.