You can try to drain all the fluid, change out the tranny filter and do a Rodney Flush with new fluid and see if you can bring the tranny back to life.....i would do that before you go down the route to source a new tranny.
When you drop the pan, you will be able to tell if you have excessive...
Hate to say it, probably need a new tranny. pull the dip stick and i bet the tranny oil is burnt. You can turn the car off and let it sit and start up again and you can limp a few hundred yards....did you overheat the tranny at some point?
Sounds like 100s is more of your Jam, considering the type of questions you asked in your OP.
IMO, if your not going over 35s at the very min. 100s is what you are looking for, with decent power V8, relatively quiet, Cruise control etc, and have enough sound batt./ insulation to have normal...
I am runnning a Derale tranny cooler made for a diesel rig. It is a little more compact than the factory unit, but it cools a bit faster and is thicker as well. And yes, the secondary cooler under the radiator is important in stabilizing the tranny fluid.
you can visually inspect the intake tube by removing it and flex it and see. No need for a smoke machine really. Also have you change your O2 sensors?
I would start with those. Having a cracked intake tube would most likely result in rough idles...
LOL. Wishful thinking. I have been rescued total of 5 times by Jeeps in the last 8 yrs, so i wouldn't say my 25+ old rig is more reliable as much as i hate to admit.