I will try to answer some of your questions but take some of what I say with a grain of salt since I've only been at this about two years.

4) yes you can just use the de-priming tool to remove them. Just go nice and easy.

3) You're going to need a oal guage that measures the distance to the lands. Hornady makes the tool now called a Lock N Load OAL guage. You'll need the blanks for you rifle too or you can send fire formed brass to Hornady and they will make the brass fit the tool.

2) I shoot three shot groups and when I get a good one I try to get it to shoot a five shot group. I'm not sure you need statistical significance unless your shooting way out there. Like past 500 yards or so.

You'll have to wait on one.

Tom