When the a/c is on it kills the engine

the 4.0L engine?
is this engine cold or hot.
why is 2000 rpm wrong for 60mph., (depends on engine and axle size and what gear you were in , then)

the idle speed for hot is too high
did you scan the PCM yet?
if hot , idle is high, is the thermostat holding water temp 180f or above. ? if not that is the problem.

Should idle between 550 or 650 RPMs. If it wont stay running under 1000 RPMs there is something wrong. Idling at or above 1000 RPMs it' going to be slamming into forward and reverse.

I doubt the two problems are related.
The computer uses an idle speed control valve to regulate idle speed. The valve controls the amount of air entering the intake.
You should have a check engine light on and also a stored trouble code for the valve. It could also be a problem with the throttle plate in the throttle body.

Usually with a new pump, Engine off and belt off, I take the return line loose, aim down into a container, put in new fluid, rotate the pulley with my finger, fluid comes out of return line, when fluid looks clear, I consider it good. Is that the way you do it?
I can't say that will work on every year--make--model, but, it seems to work for me.
If no fluid, have to check power steering lines and rack. Just my opinion.

replace the iack (idel air control valve) this controls you air to fuel mixture when can is just idleing
when you use the gass peddle to keep rpms us this over rides the iack just replace it and it should be ok

mass air flow, coolant temp. sensor possibly

1993 s-10 should have a 4.3 engine. Your symptoms tell me your throttle body injector is clogged, and only allows so much fuel to pass through it. Therefore, on a idle there is not enough fuel coming through to keep the engine running, or to start it. If you replace the throttle body injector your issue should cease.

I hope this information helps you, and I wish you luck on your repair.

There's probably a little vacuum actuated valve in one of the hoses going from the engine block to the heater core. make sure this valve is working.

Also... check coolant level

and

Your water pump may be marginal, only circulating adequate collant at engine speeds above 1000 RPM or so.

have tried tried changing the inline fuel filter. If I remember correctly it is in the tank, but I had issues with mine not getting above 20 mph and have almost no acceleration.Come to find out, it was my fuel filter that was so clogged that almost no fuel was making it to the injectors.

is car running on all cylinders pull plugs and check condition