1.
Original empeg tuner is smaller as it uses surface mount components. Patrick's tuner is all throughhole components which are easier to solder but bigger.
Original empeg tuner has sockets which are flush mounted on the casing. Patrick's tuner has them on the end of a lead.
Original empeg tuner has a dial to set the tuner ID. Patrick's tuner has jumpers inside to set the tuner ID.
Patrick's tuner has the ability to later add an IO expansion board. Original empeg one doesn't. The expansion board hasn't been made yet though.

That's about it really. The main difference between the original empeg tuner and Patrick's one is that Patrick's one is bigger. All of the other differences aren't that major.

2.
Ask Rob probably. Not going to be cheap though.

3.
Nothing major. Just adds support for the poll syscall on the audio device.

- Trevor