Well I've tried a few different things so far:

1. I ran water over all the different joints in the suction side piping while watching the return jets to see if the bubbles diminished at all -- they did not. The pump lid still continued to show a lot of air.
2. I used smoke around all the pump joints to see if any was getting pulled in -- none. Checked around the pump lid as well. Relubed the gasket just in case and closed the lid snug but not too tight.
3. I applied a high temp waterproof silicone around all the PVC joints on the suction side to rule out air leaks despite the lack of indication from the previous two strategies, just in case. After allowing it to cure all day, tried the pump in the evening and the problem remains.

At this juncture I am beginning to suspect an in-ground leak somewhere but have no idea what tracking that down entails or whether it's even feasible for someone like myself. I appreciate any and all feedback in this matter as it's beginning to look like it might get expensive and we really can't afford to throw too much money at this yet considering our recent move in and related expenses. Thanks so much!