Sorry to hear it resulted in such a roundabout process of elimination to determine the problem.

It doesn't sound like this is why your A/C system was overcharged, but your story should be a cautionary tale for anyone putting too much faith in the accuracy of the gauges on those DIY A/C recharge kits as opposed to having an A/C system professionally checked out and recharged if necessary to make sure both the high and low sides of the system are operating with the proper pressures.

It just so happens that my A/C system seems to currently be in need of being checked since the cooling doesn't seem to be consistent, but as long as a proper charge adjustment should last, it's well worth the $60 or so to have it checked and charged accurately.