It was almost like it was sucking the air created from the boil and wasn't able to get enough liquid. As soon as killed the flame, it immediately pumped at full volume.
I also lost my dip tube, and I believe this happened when I initially started the recirculation. I recall hearing a pop, but I attributed it to an air bubble or something. Is there some weird physics happening here?
All the symptoms sound like pump cavitation problems.
Noise is one indication, flow rate change, pump vibration, shock waves from the vapor bubbles, etc.
Preventing pump cavitation:
Lower the fluid temp, increasing the pressure at the suction side, check pumps data sheet and a GOOGLE search "Pump cavitation definition".
A pump is a very interesting subject.