Dexcool sucks. Do a google on it and you'll see hundreds of thousands of hits on it. After you flush use the standard green stuff or better yet a non toxic antifreeze. You might also want to pull the heater core hoses off at the block end to flush out the core and hoses good.
The hard start and stalling is probably not related. The 4.3 is real sensitive to bad gas and carbon build up. When ever my wife would complain about hers doing that I'd trade vehicles for a awhile and run to or three tanks of Chevron or Firestone gas thru it. The additive in both is called techroline and if you can buy it at the parts store if there isn't a Chevron station around you.