Just thoughts.... I am 6'1", and just went over 200 a couple weeks ago. My Quads are not as big as yours, but that is due to my stubborness toward Squats, which I JUST overcame a month ago.
I am 20 years older than you are, and have just come to the point where I can now add some serious weight. I started 30 months ago at 162, and have slowly added. BUT, at 203 today, I am still too lean.
I didn't read your whole post, but looking at your pictures, I wonder about something. I'm sure you don't do this, but I did. I used to do 12, 15 reps a lot, sets of 4, etc, etc. I got stronger, and very lean, but did not add the mass I was looking for.
I base my training on HIT. (NOT HIIT) I workout off of dorianyates.net, and if it is a chest day, I do his chest routine. I am in and out of the gym in 40 minutes or so. I lift about twice as heavy as I used to, and that has made a huge difference. Part of it was my mental image of my 162 pound self, but I am now comfortably pressing the 105 Dumbells, 4 full plates per side on Hammer stuff, etc.
If you keep your metabolism high, which I definitely had, will that keep you from gaining mass? At 6'1", I need to stop at about 225 or so. You are 3 inches taller...I would think you would look much better at 240.
I know everyone thinks chest first, but I am still pretty skinny looking, and my arms are about 1.5 times what yours are. They need to be bigger.
You have a very lean look, and you seem to be very active. I am not sure you can add the muscle you want to, without purposely slowing down for a while and letting yourself grow.
Try not to take comment personally. Understand this site is full, FULL of Testosterone. It comes with the territory.
Last. I would hope you ride a Ski Doo, or at least did, back in Wisky. I covered most of your state when I was younger, dodging deer and running 65 mph through the woods to the next stop for a cold Pabst !!!!