Cleaning up GND/PWR-plane air wire errors in EAGLE + bonus questions
I've finally figured out why Eagle isn't happy with me; the air wires are a complete brainfart — sorry! Obviously SMD component don't punch through to those layers, and thus have to be routed. Taking a break from things allows one to see such things a lot clearer, and I had been working tirelessly for two days straight — haha! :D

Any further comments and advice on finishing up the board is welcome! Thanks! :D