Water in the cab

[Waterloo]

Well, could be from around the windshield. Is that a gasket holding the glass in or is it butyl?

Also where the visor attaches to the roof, that could also be a possible area that water gets in. The other area is around the roof line where the cab roof attaches to the body. Check around those A pillars up near the top of the doors, there is a seam there also.

Our ProStars like to leak like that, I used a case of silicon caulk all around the roof line and where the visor attaches to the cab roof. The leaks have stopped.

The water when the AC is running is something different, sounds almost like the heater core is leaking, but you said it is water, not coolant. Condenser does not sound like it is draining to the outside. I know you said you checked the drain, but maybe something got up in the box and has it plugged from there. Have you gently used say a coat hanger to push up into that drain, all the way into the AC box to clear any blockage? You may have to pull the dash apart to physically get into the condenser box to inspect and clean.