1, 4: If you can get your hands on a tensionmeter, that would aid you a lot. It's very simple to use as if you read the instructions it comes with.
4a: Use the tensionmeter as a guide to get your spokes into a good tension range of about 100~115kg/f (depending on rim) and make sure the spokes are all within 15% of that range. For a dished rear wheel, get the drive side to desired tension and have the non-drive side spoke tension high enough that the rim is roughly centered in the frame.

2: Usually the non-drive side spoke tension is about 65~75% of the drive side.
3: only when you've completely lost track of what you're doing, since starting off from scratch is unnecessary once the wheel is properly built.

6: the nipples are nuts and the spokes are screws. They have the same thread direction as normal screws, BUT you're looking at them from the back side so they have to be spun in reverse in order to get the desired tightening/loosening.


since a trek portland is a disc brake equipped bike, I'd only worry about getting the tension even on the spokes. Not very important to have the rim perfectly straight or round when compared to even tension.