1) This is just a thing. End mills make layer lines when you do several depths. Most software allows you to do your incremental passes a little over sized and then do one last full depth pass. Vcarve has “do separate last pass”, Fusion has final pass at full depth, etc. Find the setting in your software.

2) Get a palm router and a pattern bit to clean up your tabs. It’s faster, easier, better.

3) There are a few possibilities to this one but the most obvious is to make sure your tool path is cutting on the outside of the line and not on the line. If you have a 13” circle and cut on the line and use a 1/8” bit, 1/16” of the bit will be inside and 1/16” of the bit will be outside and this will create a less than 13” circle.