Your doing good. It's a long road to get where you are at when figuring it all out on your on. I am still on this road just a little way ahead of you. I graduated from your 16$ tool to 0ne that measures caster and king pin as well. By the way you can actually measure your caster with the gauge that you have. I made a holder for that very tool out of a piece of angle iron cut to the length of my rim lip to lip. cut 2 more pieces of the same angle iron about 7 " long and slid them behind the rim with a long bolt through the longer piece at the top and bottom so when you tighten the bolt it holds the longer piece snug to your rim and is rigid to give you a true reading. Center your gauge as if to do a camber reading and 0 the gauge. turn the wheel out and read the gauge. turn the wheel in and read the gauge. Subtract. The # that is left is what your caster is. You will find that when you get your caster set even within a degree your camber will follow a lot easier. The string set up is still to date the best way I have found for setting toe. I hope this makes sense and helps. Your on the right track. This alignment course is not an easy or fast class. The good news is that after you get toe, camber and caster figured out it's like an infill commercial "BUT WAIT!!!! THERES MORE!" Just worry about those 3 and you'll be fine. You're close.
This means a lot to me. Thank you.