Sounds like you may have a problem with the idle speed control. My '87 (4.0l) always seems to idle in the 700 rpm range regardless of whether the A/C is on, or the tranny being in gear or park. Sounds like the idle speed on yours is not being increased as the load on the engine is increased by having all the accessories on, and it finallly stalls out. I've had issues with the idle speed in the past caused by dirty connections. I ended up cleaning the connectors for the idle air control, the throttle position sensor, and C101 connector by the brake booster. Cleaned and filled them with dielectric grease, no idle problem since (knock on wood).
Lights dimming etc. at idle may be normal (mine does it too) if you have everything on. Alternator can't keep up at idle speed, and if your idle speed is lower than specs, that will even make the alternator output that much lower.
So my .02 cents is to make sure the belt is in good condition and properly tightened, battery cables clean and tight including the engine block and body grounds, and get that idle speed checked out !!
:repair: