Awesome job writing this up. Congrats on the 1M, looks awesome!
I too did the same type of road trip to pick my beloved M3 late last summer. I saw the exact options/color combo I wanted in Virginia on a Ad posted on the M3 forums. Immediately I contacted the owner and called up a buddy and booked 2 tickets to DC as well haha.
Picked the car up and had an epic cross country road trip back to Dallas, TX, through curvy/scenic roads. I wouldn't have done it any other way. I got to know the car I purchased very well, got to spend time with a good friend, and to drive cross country. I would absolutely do it again, as I am sure you would as well.
I was going to make a thread similar to yours, but never got around to it! Awesome thread, lots of win!