1997 tahoe

i started my tahoe this winter only to find out my antifreeze level was to low. so needless to say i had problems. it blew out a plastic tank on my frozen radiator and also sheared off the shaft in my water pump. so i replaced both and the thermostat. then i got it running after about 2 minutes it died and would not start.... so i hooked my wifes van to it and gave it a jump... it restarted, but after removing the cables something kicked in and it died. so i repeated the jump process... same thing it died. but while it was running i noticed it only read 12 volts on gauge, like the alternator was not running ,so i took it in to be tested and the shop says its fine,, so i went back to the battery and charged fully and now truck will stay running although only with 12 volts on guage and it runs terrible now ,on idle it sounds fine ,but when i give it gas it almost acts like the old distributor caps did when they would get old or a little moisture in them.. any ideas can u please help me!!:disappoin