seat tube ctc 17.5
seat tube ctt 20.0
top tube ctc 22.0
TBH, I kinda knew I was right about size 20, even though I'm many thousands of miles away. I have a ruler on my desk and to help a pal it's not too hard to place said ruler on my PC screen along the line of the tops of the tyres. It's a fact of geometry/arithmetic that there's just under 15" of seat tube below that line, so you can estimate the c-t seat tube from how much there is above the line.
Those dimensions actually look very good for you, even though size 20 might not sound too promising. The top tube of 56cm is quite short for a size 20 and is in fact the same as a size 18 Kona such as the Kilauea SE. And although you don't give the head tube, it looks to be c15cm, 4cm more than the Kilauea. That sounds like a good combination for your back. The only downside is the higher top tube - 2" higher at the back and 4cm higher at the front.
And on the geometry, the bb drop looked a bit small with the Pace on it, indicating that the Pace was too long for it. But the Pace is a long fork, so I expect it'll look a lot happier when we see it built up with that Rockshox.