Using the RR2150's sub out to the LFM-1 Compact is the preferred approach, so you're good there. Likewise, setting the crossover to "out" will disable it and let the RR2150 take care of bass management - so you're good there, too. To test the phase setting, you might try some low frequency material (pipe organ would be an extreme example) and see which setting (0 or 180) sounds louder - the louder setting would have the least cancellation between sub and speakers and would be the preferred choice.

It looks like the PSB Image 2B's start rolling off around 70Hz or 80Hz, so you might want to try using a slightly higher crossover setting. You could possibly even go as high as 100Hz, but I'd definitely give 80Hz a try.

Sub placement can be a bit tricky. Outlaw's own Peter Tribeman recently reiterated an old trick: put the sub in your listening position, play a test tone, and use your ear or an SPL meter to find the spot where the sub sounds loudest. That is going to be a good spot to locate the sub in your space. Corners are commonly used, but not essential or even guaranteed to be good locations.