You are at the point where you need a professional diagnosis. Someone needs to first hook up a scanner and monitor your TOT/MLP/TP/Sol1/Sol2 at least and hook up some pressure gauges to see what is going on. You really are past the point of throwing parts at it.
As far a MLP symptoms, I noticed there was usually a problem at highway speed, a shudder or intermittent neutral. I wasn't the trans guy but they got shipped to me for performance concerns. Easy to catch that with a scantool/recorder. A bad MLP usually will not set a code.
There are a myriad of causes for your concern. Valve body (sticking), seal leak, leaking.cracked apply piston etc. That is why trans gauges are nice, if the pressure is correct to the actuated component, thats where you look, if the pressure is not there you look at valve body and or seals.
Now that I think about it, I am glad I never had to do more transmissions than I had to.