So I fix the heater barrel, which involved re-doing the heater element. I test resistance across the heater element, (8 ohms) and across the thermistor. Then I assemble everything and hook it to the controller. When I add power, the heater LED lights up even when the heater is off! :(
Turns out I have a short between a heater wire and the thermisor wire. Didn't test for that. Doh!