Pin 2/tab of the FET will short to ground if you screw the FET down. You're probably better off just leaving it standing vertical unless there's something in the way, and ignoring the tab in the layout.
Try to get C3 as close to P+ as possible.
Place an additional capacitor (47 nF or something like that, 10 nF, whatever you've got laying around) as close to pin 8 of the 555 as possible.
Place D3 as close to the pump terminals as possible. It will fit between them - this is the best place for it.
Run the track from P- to Drain horizontal out of P-, rather than down at 45 degrees, for a continuous ground plane.
You could also make a lot of the tracks thicker, then if you leave it in the etching tank for a few seconds too long they're not as thin as your arm hairs.
The ground side of C1 is isolated from the main ground - you need a jumper, wire or zero Ohm resistor between the island of ground plane in the middle to the rest of the board ground. The little yellow line between C3 and C1 indicates that it is not connected. Pin 1 of IC1 is also not connected to ground for the same reason. You might be able to change the layout to prevent an additional component being needed.