1. The MTH signals have a separate harness for each signal and power that plugs into the controller. The signals themselves have their own, much smaller wires coming out of them. I should have included this picture in the above post.
2. The spacing is 2.54mm as you said above. I haven't yet looked on Digikey, but it's on the to-do list. Maybe if I stall long enough GRJ will be by to ID the connector type, he's awfully good with connectors, among other things. Of course looking for them on Digikey might also be interesting.
Thank you for the detailed explanations for the rest of this and I really appreciate the time you take to explain it all so thoroughly. It's a big help in learning.
This morning I was thinking about a couple of the things you covered here, like swapping the wires (VCC & GND) and also some way of switching between the common anode and common cathode modes. I wasn't sure it would all work though. You have more than covered all this and then some here. Several things that I hadn't thought of or even knew was possible or knew to do as well. Resistor value changes, turning the transistors 180 deg, adding jumpers, and everything else you pointed out.
Now if those MOSFETs would show up. I did learn something interesting here though... Contacted the seller, he said he would resend or refund if they don't show up soon. But here's the good part and an FYI (if you didn't know this already, I didn't?), he told me ebay was the one that offered the guaranteed arrival date and they would give you a $5 voucher if that date was not met. Not sure how they can do that, but I now have a $5 credit for the next electronics 'gadgets' purchase! But no MOSFETs...
I printed out your post and I'm off to the study lab for more learning and experimenting! I'll report back with the findings (or more questions, hopefully not too many).