You will want to measure the angle of the u-joint (axle side of DS). This is what causes vibrations. The angles in the CV (SYE side of DS) isn't important as long as the joint isn't binding.
There are 3 ways I've done it. I do all 3 just in case.
1st: Put an angle finder on the DS (blue arrow). Then put angle finder on flat area on the bottom of pumpkin (red arrow). Subtract those 2 angles and you get the angle of the u-joint. You want it to be 0-1 degrees if possible.
2nd: Turn DS until one side of the DS yoke (pink arrow) is aiming straight down to the ground. Put a socket up to it. Then put an angle finder on the socket. Now turn the DS until the pinion's yoke (green arrow) is aiming straight down to the ground. Put a socket that just fits inside it and put the angle finder on the socket. Subtract those 2 angles and you get the angle of the u-joint. You want it to be 0-1 degrees if possible. I have a feeling this is the more accurate way.
3rd: You can eyeball the angle pretty close to 0 degrees.
No. However, if you jack up the rear axle to get the tires off the ground, and put the t-case in neutral, you can turn the DS with ease. This will not affect driveline angles as long as the jackstands are under the axle and not the frame.
Either UCA is fine to start with.