Your current gunsmithing library looks pretty decent. I agree with craigd that "Shotgun Technicana" is worthwhile, but usually pricey when found. It may have additional value as an investment. I thought Tony Treadwell's book was available as an E-book download, but haven't seen any mention recently that his widow is still selling it.
I think the entire four volume set of Brownell's "Gunsmith Kinks" has a lot of useful info, even if most of it is not aimed strictly toward doubles. "Professional Stockmaking: Through the Eyes of a Stockmaker" by David L Wesbrook is very good. And if you will be doing any shotgun stock making, "Gunfitting" by Michael Yardley will be useful. Used copies of Tommy L. Bish's "Home Gunsmithing Digest" can be found very reasonably priced, and have some good info, even though it is aimed more toward beginners. There used to be a lot of excellent gunsmithing articles years ago in RIFLE Magazine when guys like John Bivens and Henry Beveridge were regularly contributing articles.
"Amatuer Gunsmithing" by Mills was OK, but I was a bit disappointed considering what I paid for it. And you have already seen that the Steven Dodd Hughes books are "intentionally sparse", and offer very little except nice pictures and self promotion. I wish I hadn't wasted my money on them. And that opinion has nothing to do with him recently calling me on the phone and making drunken obscene threats. Apparently, he didn't like me mentioning that he had been using this site for free advertising for his over-priced classes. Liberal gunsmiths can be awfully sensitive.
