What I do is barely seat the bullet or just measure the bullet and case together since load alot of Boattails. AFter I measue that, I set my seater high and go in a little at a time until I am .277" lower than I started with. You really want .277 or .28 bearing surface in the case not just the bullet length IMO. Then measure the length.

You shouldn't have had to FL sized. I am not sure why you would wrinkle the necks. Maybe you can explain further.

Are you screwing in your seater die until it touches the top of a case and then backing out one complete turn? Don't cam over your seater die like a sizer die. You know touching your shell holder. You want to set your die up as I explained and use the seater stem to adjust your seating.