My experience with these transmissions (limited not claiming to be an expert) is the filter is everything. A dirty or clogged filter can completely starve the pump. I'm thinking that mine has filled up quite quickly due to the amount of pollution that was in there. Also I'm thinking it then filled even more quickly after the complete flush and now that new fluid is cleaning everything inside this causing the filter to become clogged. Well find out this weekend!
And what do you think is clogging things? Automatic transmissions aren't going to be clogged by debris from the air. If you're starving the pump, its likely you've shorten the life of it and other parts.