What is wrong if a 1998 Ford Escort ZX2 surges when the AC or heat is on and also seems to overheat and stall very fast on the highway?

Your surging is probably caused by your A/C charged too high. Use your key to relieve SOME of the pressure at the valve under the hood (it looks like a tire valve). A little green liquid might be released too, so don't stand directly in front of it. Keep letting out a little at a time until it stops.

TheBobsHere says,

If your car overheats after slowing from highway speeds you may need a new radiator or cooling fan. The surging could also be caused by a bad or reversed cooling fan, or air in the cooling system (just because the reservoir is full doesn't mean the system doesn't have air in it).

Never remove refrigerant unless you know it's overfilled, plus it's illegal to vent refrigerant to the atmosphere.