I can answer one of your questions. The kick down linkage/ throttle pressure linkage being unhooked will cause damage.

Most make it sound like the transmission will burn up if you take it down the street without it being hooked up but, that has not been my experience.

I inherited my car and when I received it, the throttle linkage was not hooked up and hadn't been for probably 1500-2000 miles. Once I identified how important it is, I reinstalled and properly adjusted the linkage rather quickly.

Again, the car was not mine from the last time the trans was rebuilt up until shortly before I reinstalled the linkage. Over the time I owned and drove it without the linkage, I felt like I noticed low speed slippage getting worse. I also noticed that I had a flare between the 2-3 shift but, it wasn't horrible. My car too has an aftermarket converter and there were some other unknowns so; I didn't think much about it. I drove the car another 2-3 years before having the trans rebuilt and I only really had it gone through as I had the motor and trans out. Overall, the trans worked fine and I really only noticed the low speed slippage when I pulled it out of the garage and ran it down the first road. Once it got some heat in it, all seemed fine.

During the rebuild, we found the low/reverse band was burnt up. I want to say there were some other slight issues too but, it's been years so; I can't recall all the specifics.

With the trans rebuilt and reinstalled with the same converter, all the slipping at low speed was gone so; it was the band causing the weirdness I noticed. At the same time I had the trans rebuilt, I added around another 100 HP and 150 lbs of torque. The trans has been run with this combination for probably around 2000 miles and 25 or so passes and has never felt like it did before I had it rebuilt so; I would assume that the low/reverse band being burnt and the slippage I had in years past can probably be attributed to the kick down/throttle linkage being removed for all that time.