Car stalls in neutral

I have a 2000 Ford Escort ZX2 5-speed. Before car used to stall when coming to a stop all the time. I replaced the Computer, Mass Air Flow sensor, Idle Air Temperature sensor, Idle Air Controller valve, Throttle position sensor. The car stalls when im coasting in neutral sometimes while taking a turn it will stall mid turn and ill bump start it. Mainly it will stall when im giong 60 on the interstate and theres a decline i shift into neutral and coast. Rpm’s will take a dive untill stall. In which case i have to bump start again. Sometimes the rpm’s will take a dive but will manage to pull back up. But 95% of the time it will simply drop. And the A/C doesnt work. I went to mechanic they could not figure it out at all. Previous owner was jumping power from the a/c low pressure switch to the a/c compressor to power a/c. That would cause even more stalling. When i removed their wire from one to the other both a/c and horn stopped working. Mechanic was able to fix the horn but a/c is no go. Compressor tested and good.

Just wanted to mention that at night when i can see the backlit gauges. If i press on the brake pedal while stationary the lights dim and idle drops 100 rpm then eventually goes back to normal. Also wanted to mention that via a multimeter built into my radar im getting a 14.3v or 14.4v reading. When i press on the brakes stationary the voltages drop to 13.8v. I had just recently changed my alternator because previously my battery sparked and blew a couple of fuses along with killing the alternator. Right now there is a rebuilt alternator in car with new battery. With this new alternator if i let my revs hit 6k or higher my battery light begins to flash and gauges begin to dim and flicker. Do i need to re-replace the alternator? And last time my car threw a code i copied the freeze frame data and on it, it showed the car temp to be 210F. Is this related? And sometimes when idling my car’s rpms will drop and rise over and over makes car sound like if its breathing. From 1k rpm to 800 back and forth untill i gas it. What could this be? Thanks.