This looks like a major failure of engine cooling. I doubt it actually is related to your AC problems or your A/C Pro fix. I could be significant clogging of the radiator, a blockage in hoses etc., or a failure of your water pump.
For a preliminary check for this, follow this procedure:
1. Start with the engine cold - not used for at least ½ hour, maybe longer.
2. Carefully remove the radiator cap. If the engine is still warm it MAY spray hot coolant out, so be very cautious! Check that there IS adequate coolant in the rad, almost up to the top. If there's a lot of coolant missing, that could be your major cause.
3. With the rad cap off, start the engine and let it warm up. Keep looking into the top of the radiator. What you should see is that it is full of coolant almost to the top and at first it does not move. That's because the thermostat is still closed and no coolant is flowing from engine through the rad. As the engine warms up the level may rise a little, and even overflow down the overflow tube to the external reservoir. But it still won't move much. After a while it should start to move around (thermostat opening), and then move even more as the engine gets quite warm. Eventually when it is hot enough that the radiator fan keeps turning on and off, the coolant should be moving a lot inside the top of the rad, and its level may rise and fall slightly as the fan cools it when it runs. Pushing on the throttle linkage to speed up the engine should create much more flow in the rad.
If you do NOT see the coolant moving a lot with the engine hot, that really means a failure of the cooling system. You say you've already checked the thermostat. Then the suspicion falls to the coolant pump or a plugged rad.
It is not common for the entire rad and all its tubes to plug up suddenly, but it is possible. Many years ago I dealt with a few slight leaks in my radiator by adding a leak-plugging additive to the rad. Seemed OK with city driving. But shortly after we went on a 2-week vacation involving sustained highway driving, and it became obvious quickly that the engine was overheating the faster I drove. We drove over 1,000 miles at no more than 50 mph to keep it under control. When we finally got there, my brother-in-law and I removed the rad, removed its top and bottom tanks (fortunately on that car, not too hard) and found almost all of the tubes were plugged with the stop-leak gunk! We used a thin flat metal strip to push all the junk out and flush it, then reassembled. We had to do a few small fixes on the small leaks it had. Car was OK for a day or two, then same problem! We re-did the cleaning, finding lots more crud in the tubes (must have been in the engine). After that second rodding-out and flush, the car was OK and never had the problem again. But I know that a simple water flush with the rad in the car would never have got it cleared out.
I'm unsure what it could be. 
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