Unless your Oryg is bent, there's no reason it should perform poorly, assuming you know how to set a gyro up properly. I have a $10 Oryg on one bike and a $60 GTX-R on the other and don't notice any difference other than bling factor.
So now...let me try to wrap my mind around this: you're running dual cables to the rear brake and NO gyro? I shouldn't need to tell you how pointless that is. Moving on...
The stopping power of your brakes is less a factor of pad compound and rim finish than how good you are at setting them up and maintaining them. I can set the same pair of pads up to feather forever or pitch me over the bars at the slightest tap. Now for the questions...
1. A London Mod is a little machined aluminum bitty that turns a single cable stop into dual cable stops. They were invented by London Bikes and sold to Odyssey. Dual lower cables are a common setup with a gyro, but they're a ***** to set up and maintain.
2. Front brakes are only a benefit if you're committed to making them work for you. They're not going to instantly turn you into a front wheel pro. Neither is running without them necessary for learning hang-5s and Karl cruisers.
3. Since I don't know ANYONE who's ever destroyed a headset spacer I have no way of knowing.