Ground Plane for Motors
You don't strictly have to cut the ground plane. General practice is to never do so unless you have a very good reason. If your freewheeling currents are out of the path of any critical signals then you don't need to cut the plane at all. Something to keep in mind when laying things out. You can physically draw the currents out and see if they might mess with anything. Given how dense you've made things it might be necessary. Not sure how much current you're planning to put through all this.

Large freewheel currents can cause the voltage on the ground plane to hop around due to resistive drops. Having an isolated plane close to the motor connections with thick ties to the power and ground planes is a common technique for containing these large freewheeling currents.

I'm not sure how much current you're putting through this setup, use a trace calculator to see if it's wide enough to handle your current through the tie. Also, move it so that it's as close as possible to the power input to your board. All currents return to their sources, think about what path you want that current to take.

It's a little hard to read the schematic in places, however you've got generally the right idea. You want your freewheel diodes to be as close to the connector as possible so the path is as low impedance as possible. The traces could also be thicker. You've got the room, why not use it? Of course don't make them so big that soldering becomes a challenge, but that's what thermal reliefs around the pads are for.

If possible you might want to see if you can move the MOSFETs, capacitors, and freewheeling diodes closer together to provide a tight path for the motor's freewheeling current.

Having the capacitor connected where it is will allow the high frequency components of your switched motor current to pass through it. Just make sure it can handle that. 

Other than that I'd recommend cleaning up the fills so they more nicely go around that screw hole.