1966 Dodge Dart

GGs66GT, thanks for taking the time to go thru everything. Im sure some of it is confusing because i screw things up as I write!
A quick update, I am still wet sanding and have everything done to 1500 grit except the side drivers panels. Im thinking I should go to 2000 then 3000 yet but was told I should be ok where I am at. I hate sanding but want it to be nice. My concern is howdo I know if im getting to close to going thru the clear coat? The Nason I had sprayed said to only do 2 coats. I wish I had put more on but I followed the instructions. So does anyone know if theres a way to tell how close you are to sanding thru?? And from your experiences is it worth sanding with 2000 then 3000 to get a better finish?
Thanks Rod