Why does the engine not stay running after removing the battery cable while engine was running?

I pulled my positive battery cable off while it was running, then turned the car off, I put the cable back on the battery and fastened the post. I read online that it was how to reset the theft traction control and gas and temperature gauges. Now the car will fire but will shut off almost immediately after it cranks. I tried to give it some gas and it really shuts off then, it's almost as if the fuel pump isn't putting gas in the lines or maybe it erased the idle info out of my ECU, and I just read that pulling the positive cable and not the negative is a really bad idea, can short out my ECU. I just spent. $7,000.00 on this car, and I have no scan tool or the means to pay $800.00 for a new ECU. Does anyone have any good advice as to how I can correct this issue or at least how to find out exactly what needs to be fixed so I can drive my vehicle? Thank you