That's a great looking build! It's coming together very nicely. I love the fact that you've built your own phono preamp. I took the lazy route and bought a Technolink TC-754 that I plan to incorporate in my build. That will give me a phono preamp, switching for up to 3 more inputs, and volume control. I'll hook that up to my TPA-3116 board and Raspberry Pi with IQaudio Pi-DAC. The form factor is quite a bit different from your build, but I won't say any more until I'm further on in the build. Want to keep it a surprise. I'll post pictures soon.
I had no idea that I could power my Pi using your technique. I may have to try that. It takes USB out of the loop and may solve some noise issues. I'll try one more possible solution first, then we'll see if your way works.
Keep posting updates about your build. You've taken some great pictures that have given me ideas for my own build. Really appreciate the information.