Two ideas on the stop-up.

Could have been a piece of plastic or something from manufacture, or a bit of plastic bag, etc. that made it through the cabin air intake plumbing if you don't have a cabin air filter. Or debris from inside the car, when air setting was on recycle.

Or could have been mold buildup. Had a minivan once that had water pouring out onto the floor. Crawled underneath and found the condensate hose easily. nothing coming out anymore. Took a length of weed whacker plastic string, doubled it over into a hairpin, and pushed the doubled-over end up into the hose, all the way up to the evaporator. Since it was doubled-over flexible plastic, I didn't have to worry about possibly damaging the evaporator.

Water suddenly poured out with a big "bloop"! Some of it did not smell the best.

Long ago, we got into the habit of shutting off the A/C right before arriving, letting the fan run with temp control to Cold, but A/C OFF, to help dry off the evaporator before parking. This solved the smelly air that would come out the next time we would get in and run A/C, if a day or so had passed by in the interim.

Mold loves the environment of car and house A/C evaporators!

If it were me, I would be very leary of blowing 40 PSI up onto an evaporator core, don't want to stress or damage that core, as cars and trucks of these days have the evap way up inside the dash, not out under the hood like they used to be! It is a big job to pull and replace a evap core behind a dash.