hi,
I finished this build last week, it's still fresh in my mind.
I'd say there is too much solder on many pads. Soldering joints shouldn't look like a ball, but more like a cone.
You can easily correct that with a desoldering pump (it can get dirty, so you'll need to clean the board after with a clean hot iron, moving quickly). To get a good cone, you have to touch the component's leg with the iron, while you move it away from the pcb.
The loud hum can come from a wrong wiring on the audio jacks, a ground problem, or a short somewhere.
If there is still a problem once you have improved the soldering, you should post a picture of your circuits inside the enclosure, with everything in place, to help us spot the cause of your trouble.
Edit: you may have a short on the switchboard, on the pads located between the Led and the footswitch.