Hey, glad to hear that they found the root cause of your tranny issue. I would NOT suggest the ACT prolite as it is too light and will cause issues starting from a stop. The street lightweight flywheel is the better option but is a bit more expensive compared to the kit in the link below.
I have some experience with a stock clutch and a lightened flywheel/F1 racing lightened flywheel for an impreza 2.2.
It was just as smooth as a stock clutch and flywheel but I was able to shift faster because of less weight of the flywheel, less weight and momentum = slowing the engine down just a bit faster when I pushed the clutch pedal in.
I would do a new stock exedy unit and a lightened flywheel like what is in this kit.