For the Freq adjustment, I tuned the radio to the loudest WWV broadcast (which I think in my case was 10 MHz) This could also work with any strong-ish broadcast station, but the tones on WWV are easier to work with. I used two pairs of earbuds. With one from the uBitx in one ear and one from my Icom-7300 in the other ear, I adjusted the setting until the pitch matched without a beat-wavering tone or as low as possible.
For the BFO adjustment, I just tuned to a strong SSB signal on the Ham bands and adjusted it till it sounded "right" to me. Believe me, once you move around with the setting you'll know when it sounds good.
I hope that helps.
Incidentally, my 1/8" jacks protruded enough for the screw on nuts, and my volume control fit fine. My board lined up with the holes enough for it to work, and I didn't really need the BNC nut.