Here are some more details on those things that I have more information on.
F450 Frame Dimension
But since you are using a 4in1 ESC you will not need to use any of those solder points as the 4in1 ESC has all of those things built in.
As for the brush-less motors, it does not matter what order you connect them, you only need to swap two of the wires if you find that it is rotating the wrong way around. That is probably why you could not find much information about the connectors.
Lastly in terms of setting up pixhawk and connecting everything to it, I suggest you have a look at the manual here
If you do have any questions about something just let me know and I will try to help.