Driving it when it loses power like that is potentially very bad if the trans is going through a possible starvation of fluid. Sounds like the trans filter could be clogged, if it were mine, I would drop the trans pan and replace the fliter and the 4-5 qts from the pan drop. Don't do a full trans flush just yet, see if this helps.
Get a deep pan filter and if the trans filter pulls down with some resistance, then don't worry about replacing the small round seal as of yet.
Hopefully the clutches aren't burned up and the 3-4 clutch pack is generally the first to go. I would not drive it anymore until you do this.