To answer some of your questions;
The female connectors - make sure you buy 2-3 extra of each one because they are so small and delicate that i broke a few in the process. BMW also doesn't stock them so it was a pain to have to wait for them to come in (usually 2-3 days).
For EACH seat harness (your car's harness, not the seat) you will need to do the following:
1) Add a power wire by connecting one end to the female connector that goes into the harness and the other end should be tapped into the fuse box behind the glove compartment (30A fuse).
2) Add a ground wire by connecting one end to a female connector that goes into the harness and add a ring terminal to the other end which will be used to mount into the same hole as the seat.
3) If you have power bolsters like mine, you will need to add a splitter into each of the above wires and also route them into the car's harness (e.g. you will have 2 power female connectors and 2 ground female connectors now in your harness instead of just one of each)
4) Now you need to add kcanbus wiring to your car's harness. I found that the easiest way to do this was using 14 guage speaker wire as it already has positive/negative on it. Follow the wiring diagram and wire one wire into each terminal using the BMW female connectors; the other end will have to connect to anywhere that you can easily locate with kcan wiring (i believe it was green and green/orange). I found it right near the same fuse box i used for the power wire. Simply tap into that wiring and you're good to go!
5) Have a beer and celebrate cuz you now have powered seats! You'll also realize how happy you are with using oem bmw harnesses instead of some other members who hardwired it because now you can swap other seats if you get bored with the existing seats and you don't have to redo all the wiring.
Current: 2015 535i X-Drive /
Dark Graphite II /
Black Dakota Leather
Retired: 2007 328xi /
Montego Blue /
Black Novillo Leather