Thank you all. My answers to your questions are:

1. The flow seems strong when I run it at high speed. As mentioned earlier, that's after 95% priming.

2. The filter pressure is 27 psi at 3000 rpm, 29 at 3100 and 31 at 3200. I think the pressure was 10-11 psi when running at 2000 rpm. I have Sta-rite system 2 PLM 200 cartridge filter (200 sq ft). Haven't cleaned it for about 2 years since I didn't notice significant increase in filter pressure yet. I plan to do it before opening the pool this year.

3. I tried to open the filter air valve after turning on the pump. Not much difference observed. I see intermittent clusters of small bubbles coming out of the returns but they seemed to stop after a while.

I decided to run the pump at 3000 rpm for hours and see if that makes any difference. I'll update this afternoon.

Based on the fact that water level in the pump basket is lowering very slowly, it looks to me that pump not being fully primed is a different issue than the air leak? Or are they actually same? Should I suspect clogged suction line as well?

Thanks again. I really appreciate your help.