Getting back on topic............

That backfire could have disrupted your transmission vacuum modulator valve so that ATF is being drawn into the intake manifold and causing that white cloud out of the tailpipe. A rich mixture out of the pipe is black, not white.

... and regarding your running conditions, I think you successfully isolated the problem to the ECU and/or the connection to the ECU. Rather than to replace the ECU, you might try opening it up, pulling out the boards, and reflowing all of the solder joints with a 30 or 40W soldering iron. ZTrain fixed his ECU that way. Thermal expansion and contraction, combined with harsh vibrations, can cause these solder joints to go bad throughout the decades.

I agree about the AFM. Give it a good check-over. If you bend the vane, your mixture will be waaaaay off. That happened on my old '75, and I didn't get the mix straight until I carefully tapped the vane back in shape with a hammer.

I will definitely give both the AFM and ECU a good check over this weekend. I'll have the time to take them off and really look them over. I noticed my vacuum doesn't have a check valve, which would explain the backfire pressure. Called the local auto parts store and they don't have one. Guess I'll have to order one online. If I can't fix the ECU and AFM I will replace, but hopefully I can find a good used ones, don't know if I can afford the prices for them new. I seen those prices and said... ouch.