Having recently started playing about 1 1/2 years ago, I am learning to improve. I purchased a table, a few cues, and started to learn how to play. I watch videos on line, of pro's, and amateurs. I watched videos on some aiming systems. Tried them, but with not so good results. Then I saw a video about the Ghost Ball. Wow! That one works for me. I came up with my own aiming system prior to the Ghost Ball with mixed results. Just wasn't consistent enough.
As far as how do you tell if you are getting better without instruction. It's obvious. When I started I would pot 2-3 balls if I got lucky with ball position. Now I'm potting 4-5 balls most of the time. Sometimes 6-7. That is improvement. Improvement I can see. Practicing 5-6 days a week, for 2-3 hours a day(minimum), for a year and a half, has improved my CB control and that has made the game much easier for me.
I now try to use as little English as possible. I get the ball to go where I want by speed and natural deflection.
Sorry I know this doesn't answer any of the questions that are in the original post, but I felt that other reply's had gone off topic and I wanted to address some of those thoughts.
Noah Buddy
I used Ghost Ball from the time I saw it in Ray Martin's 99 Critical Shots in Pool until I learned CTE. Now it's all I use. That should start a shit storm.