The coolant gushing out of the rad tells me you do infact have air in the system.

How much coolant did you put in? Whats the capacity?

While its running and hot, try burping it from various hoses like the upper and lower radiator hose. Loosen it until coolant pours out a bit.

Also, looping at idle but OK at speed indicates a vacuum leak. Sometimes it can be VERY difficult to find, especially a crack in a hose or intake tube. Get a can of ether or a propane torch and spray around the intake tube and all the vacuum lines, and see if the idle smooths out or increases. This indicates a vacuum leak.