1993 Explorer.A/C is full of hot air and in hot water.

1993 Ford Explorer, V-6 (4.0) 185K miles, automatic, 4-wheel drive. A couple problems which all may be related. The A/C is fully and properly charged with R134-A (converted over from R-12). At hiway speeds, a/c is cold but not as cold as it could/should be and engine temp is basically normal. When done with hiway and driving the local stop and go streets, a/c temp warms up. Say about 15 degrees below the outside air temp and the engine temp is very hot. Temp gauge is now centered between "H" of overheating and midway of the gauge. (Like 3/4 of a tank of gas or a little higher) While sitting at a light, air out of vents gets oven warm, maybe equal to outside temp. Once u start driving, the a/c air begins to get a little cooler (slowly). All above info is during daylight hours. At night, the a/c gets colder and the engine temp comes down as well. Next part.I noticed today that while I was driving, heater control (manual) is off and temp control all the way to the left (cold) I am feeling warm/hot air coming out my a/c vents. Feel nothing at stand still and the faster I drive, the stronger the airflow coming out of the vents. I am thinking that maybe some door that should be closing on the heater box, is not fully closing or visa-versa with opening but not fully opening. In 2006 I had the a/c's heater core, think its called the evaporator replaced because of broken tubes which left the system open to the atmosphere for about a year. A/c was not very cold so the receiver dryer was replaced (the aluminum canister) to correct that. It really didn't seem to improve it much. Not sure if the orifice tube was replaced. Not sure where the orifice tube really is. Would the orifice be located in either of these 2 parts? I am hoping that all these symptoms share a common solution. Any suggestions you can offer me would be GREATLY APPRECIATED, seeing that I am burning up from all this hot air.

Ray