Badger, you put so much care in this decision I'm not surprised that you're probably still thinking of some of the cats that you took a really close look at, as well as the bigger picture.
The reality is you can't save them all. This is probably an overwhelming decision for anyone who visits a facility like you described.
I think as you and your folks spend time with Boo and he gets accustomed to his new home, you'll know you did a good thing.
For anyone interested, I dug up this old article about strategies that some shelters were using to promote adoption, especially of black cats and dogs.
2014 Bobbin Bramble / Brooks B67
2008 Rodriguez Rainier Mirage / Terry Butterfly Tri Gel
2007 Dahon Speed Pro TT / Biologic Velvet