YES...
to most of your questions---
1. yes i measure through the center- cut the border and add it----
yes, i have added borders to the sides then trimmed them to size
2.yes- when necessary i 'adjust' the size of a border to fit the bed
3.yes- when piecing borders i adjust the blocks to fit-
yes- sometimes i have to add (fudge) to make a border work
4. yes- when mitering multiple borders i stitch them together then do the miter- if that works for that project- if not- i add/miter individually
5.yes- i've made varying size strips in a piano key border---yes i liked it
6. yes- i use corner blocks if the quilt calls for it- yes i miter corners if the quilt needs that type of border- and yes i overlap borders on some quilts
7.yes- i've used prarie points --- you trim the bulk
so see- each quilt is an individual- each needs/has it's own needs- there are no wrong answers= you can make your quilt any way you want to achieve the outcome you are seeking.