power & GND plane on two layer PCBs
Power planes are almost always a waste of real estate, and certainly on a board with only 2 layers. Track the power, let signals share the space.

Breaking a ground plane, that's if there's only one, is almost always a no-no. If you're going to the bother of using a ground plane, use a whole one. You don't need to use two for this speed of board. If you do want to run a track through the ground, then stitch the ground together on the other layer.