Your hard shifting tranny at WOT is caused by a engine that is not putting out the power expected at that throttle setting. The trans doesn't know any better and it has the pressure all the way up to handle the power expected to come through.
The trans pressure follows the TPS voltage. (throttle position sensor) The assumption is that the power from the engine is matched by the pressure it needs to make the shift. When the engine has performance issues, there is a mismatch of the power vs the trans pressure. The original settings, were for the horsepower that the engine had, when it left the factory. It may be a little less now.
The trans is not the problem here. The engine needs some work and if it is actually at 250,000, it most likely needs major work.
It is very unlikely that all of the door locks failed at the same time. Look for a common denominator. The switches are the weak link. On DC circuits every time they are actuated, there is a tiny spark. That spark leave residue that builds up. After a while, that residue begins to insulate the contacts more and more until it just will not work at all.
Most of the GM switches I have seen, are not servicable. New switches are easily found and are easy to replace. You can always uses a jumper wire to prove the switch is the culprit. If you are not sure of wiring, have a fuse in the line of your jumper so you don't fry something.
Good luck.............:thumbsup: