I'll try to tackle this one, but I know there are many more knowledgeable people that me on here. :)
1. Rein stops are for use with a martingale, so the rings don't slide too far.
2. Rubber bit ports ??? It looks like it's supposed to keep a horse's tongue from coming up over the bit.
3. Dee ring savers attach to the dee rings on your English saddle, and you attach your breast plate to them, instead of directly to the saddle.
There are generally two reasons that I wrap a bit with latex bandage. I show appaloosas, and at shows, twisted wire bits are illegal. So if you have a twisted wire bit, you can wrap it and it becomes legal. You can also wrap a curb chain if you need to. The other reason I wrap bits is to make a bit softer. When I am lightening a horse's mouth, it can be helpful to wrap a bit (especially the twisted wire ones) because the mechanics stay the same, but there is less bite.
I don't know if I made any sense or not, LOL. It's late, and I'm tired. I'll check in the morning.