It was the 12stockwelljoanne12 account, which predated SSB9's infamy. It was his "Joanna Tang" character's account, the one where we
actually know whose photos he edited.
I'm not fully convinced he was actually identifying himself in that video, considering the whole account was him LARPing as someone else anyway. It seems just as likely he saw some teenage girl in the clip and pretended he was her, too.
Yes, I've begun to think the same after a while... it just seems a little too good to be true, and also a longshot that he would even be aware that he was caught on film, let alone find himself in a random YouTube video. It's probably more likely he was trying to pretend he was a girl in the video. Right toward the end there are a few younger girls that don't look
terribly dissimilar to those on his account. From
right before the very end:

Recall that he elsewhere posted a very unconvincing AI video on his Stefanie Schoolie account saying, "some are saying this is not really me, but here's a brief clip of me saying hi!"

The Brixton walk video strikes me as possibly the same thing--not him actually revealing his identity, but rather trying to authentic his identity as a child with fake proof. Who can look at a 40 minute video with thousands of people walking past and say, "Nah, you weren't in that!"?
As far as the church issue, a possible theory was that David was trying to make a bit of a name for himself in the church and had to be put back into place. His response to David Bedford includes this snippet about a cassette tape.
As I've reread this, it seems like perhaps David was mailing cassette tapes of himself around. After all, we know he likes to create his own media--weird fetish stuff, but also songs, etc. Also, he saw cassette tapes as essential to his own spiritual development, listening to recorded messages in lieu of attending at one point. It wouldn't surprise me if he tried to "make it" as some sort of teacher of United Church of God theology via cassette tapes. A bit delusional, but he tried to make it as a lyricist and wasn't good at that either.
The subtext of this anecdote is that he sent the cassette tape to someone, it got into the hands of Duncan McLean, presumably another leader in the church, and then David Bedford and McLean paid David a visit because it "sounded like someone starting his own church." It seems like perhaps McLean brought Bedford to David's acquaintance in the manner of, "This guy is causing trouble and passing out cassette tapes, can you set him straight?" If he continued in this vein, later trying to raise money for his cassette tape, that could be the reason for the popping up in the bulletin, if the church went to the police and said, "Hey, this guy is a fraud, will you tell him to stop trying to raise money from church members?" Conjecture, but perhaps Fenney will respond and we'll get a bit more of the story.