Q: My car overheated i believe and was jerky

My heater for the last couple months would blow cold at idle and the higher I revved the engine the hotter it was. A couple weeks ago I had the valve cover gasket repkaced,thermostat , upper radiator hose, ETC . last couple of days the heat wet out all together and blew cold and would come back hour 5% of time driving . I checked radiator and was dry after I had it flushed and filled 2 weeks ago, I filled it and my heater turned on full heat and was driving good get in it 3 hours later and it has lost power between gears but engine is performing normal. I get on freeway going 65mph and my temp light comes on ( I don't have a needle just red temp light ) I pull over and car started jerking violently turn engine off and on and temp light is off turn it over again and idles fine drive 10 seconds and jerks again. I put coolant in again and made it home fine no problem I notice white corrosion under the cap and it's flowing all into the overfill and radiator is steaming when warm suspicious

My car has 120000 miles.
My car has a manual transmission.