Wow, it's a little surreal to hear from Tagg/Tinsel when we've been reading their journey for so long!

Thank you so much for the words of encouragement.
Days ten through fifteen: I'm sorry that we've been a little bit AWOL. We've been in a figuring-out phase over here. Around day ten I started to notice a little bit of regression and a lot of plateaued progress. I know that this is normal, but I had a gut feeling that something about the current arrangement wasn't working for him. I evaluated the situation and reached the conclusion that his "spot" was too busy - too much too soon, too many people and their accompanying sounds. I did some searching and found this:
http://cynography.blogspot.com/2009/02/taming-wild-beast.html which was extremely informative and reinforced my suspicion that he needed a more controlled environment, where I could expose him to sounds and experiences deliberately, as he's ready for them.
My husband and I have a giant bedroom with a huge bathroom, a ginormous walk-in closet, and a bedroom space so large that we've converted half of it to a second living room. The cat lives in there (by choice). I decided to move him in there. The closet seemed like a clear choice to me - we're rarely in it but often near it, the door stays open, it's not "open space," and I put down a huge quilt for him to lay on and brought him in there, and...no. He bolted out and into the living area, into the corner behind the laundry basket. He's chosen this spot, no matter how much I try to move him. It scares him if we put laundry in the basket, so the bedroom is becoming a laundry jungle.
I think that he's doing better in there. Since he
will eat around me after some hemming and hawing, my husband suggested that I only feed him when I'm there so that he can come to directly associate people with food. (I had been tossing him treats during our reading him but giving him his regular food in the crate at night or under the desk, depending on how he was doing.) This made sense to me, so now I go into the bedroom living area every couple of hours all day and spend about half an hour reading to him from four feet away, sitting sideways, with the food and water bowls halfway between us. (And can I just say that I am actually hoarse from all of this reading?) He eats and drinks almost every time. It scares him to be picked up and taken outside, and I feel like everytime we go out we move back in progress and trust just a tiny bit, so I've paid close attention to his potty schedule and whittled it down to just enough bathroom breaks that he never has to be uncomfortable - one in the morning, one at night, and one mid-day if he ate or drank in the morning. This seems to be plenty for him and I think that he's a lot less stressed not having to go out every few hours.
He's still terrified. You know, it's easy to report the good stuff and then it sounds like he's just moving along at a steady clip, and it's not that straightforward. Without seeing him you just can't even appreciate how truly horrible his baseline state is. He still tries to climb up the wall when someone comes into the room. He still has only walked around the house twice in fifteen days. He still thrashes and flails and falls down, all but seizing with panic, if he catches his foot on the leash outside or just spooks for no reason. He still stays in whatever his chosen spot is basically 100% of the time unless he's bodily removed. He is in every sense of the word feral.
That said, he has been making really, really good eye contact. When we're in the bedroom, he spends most of his time silently observing us, and now will keep looking even if we look back - when he came, if we looked at him he would instantly stare at the floor instead, we'd just watch him watching us in our peripheral vision sometimes. Now, he watches us constantly, and holds eye contact. Sometimes if I look over at him while he's ventured a foot or so out of his spot to drink, he'll even keep looking at me then, and stay out, and keep drinking.
The other good bit of progress is that on day thirteen he became willing to do his business outside even if I don't sit down on the pavement. Until that day, he would plaster himself to the wall and not take a single step forward until I sat down - and not for a while, then. Gradually he started coming forward sooner and sooner after I sat down, until one day I just didn't, and he seemed to think "Well, whatever, I've gotta pee," and just did! He'll do this every time now.
I think that part of it is that he knows what that time and space and part of the day is for - we go outside so that he can go to the bathroom, and then he goes, and then we go in. It has a structure, an identifiable behavior that belongs in it. He knows what to do. I think that that could be useful for him later, if I can ever find a way to structure different spaces so that he knows what's done then. He's never been in a house or around people, he doesn't know that indoor time is just time to chill, lay down, socialize with the other dogs, get petted, chew a bone, play with a toy. I think he's terrified
and he doesn't know what to do with himself. I'm hoping to be able to bring him back into the main living space as soon as possible so that he can watch what the other dogs do with themselves.