2016 Focus SE MTX-75 shift cable adjustment

I have a 2016 Focus SE, 2.0L Flex fuel, and the MTX-75 5 speed manual transmission. I've just replaced a broken roll pin in the shift tower, the upper transmission mount & the cable bushings on the shift cables. Everything seems good except sometimes when I have it in 3rd I can hear / feel a bit of vibration up through the stick. It's in gear & doesn't pop out but it feels like the gears are lightly brushing the selector on the tower. Not every time & when it happens if I nudge the stick it seems to stop.
I've seen some instructions for a "neutral reset" or shift cable adjustment to reset the cables to the proper length. I think the white/yellow clip just before the bushing on the upper cable end is the clip I should release,
but when I tried, I couldn't get it loose. I was being very careful; it was very cold out & I didn't want to snap it as I had no spares. I've seen some videos showing how to do this, but they all have different clips.
Three questions:
1. Can anyone tell me the part number for that clip if it's sold?
2. What is the right way to adjust these cables?
3. I don't see any way of adjusting the lower cable. Is the upper (side to side motion of the stick) cable the only one that gets adjusted?

Thanks!