So dumb question but is the kickdown cable just the back end of the throttle body cable? Also would a warn/sticking kickdown cable cause reverse to not engage properly?
Yes, it is the one connected to the cam adjacent to the throttle body cable. When mine stuck, the trans slammed violently whenever I put it into reverse. Occasionally it misses the shift, but that's just a sloppy linkage issue.
Yours could be a combination of low fluid, loose linkage, and sticky cable that caused those issues. I can't say for sure without seeing it but I'd sure rule it out before spending 2k