Please critique my home front-end alignment method

Of course you do. You have a means of measuring a right angle, don't you? Half of that is 45 and half of that is 22 1/2* which is close enough.

Are you paying attention? You don't need to buy anything. If you have a means of accurately measuring camber, then you can measure caster.

I don't that you will get too much, or even enough too much to cause wandering. Most Mopars suffer from not enough with radial tires, and then you run into self centering issues, especially with power steering.
I guess I kind of misspoke. I didn't take the time to make or buy anything that would give me an easily repeatable way of turning 20 degrees which is why I was using the steering stops. Although it sounds like marks on the garage floor could work very well. I also think I might trust a bubble level type device more than my cheap digital angle gage. Sort of like stringing the car for toe. I looked at a relatively cheap laser to possibly use and the accuracy was only like +- 1/8" in 20 feet. I know I can get closer than that using a string.