I think it's possible that he did hit the wall and yell and Jayme to scare her at various times when he was angry. I don't believe that would preclude the hitting her on the back.
His account of the hitting on the back may be in the sealed documents. We don't know whether he's told about it or not, IMO.
Also, he told so very much to police that we do know about from the Criminal Complaint doc., but he never says anything like " Taking her was a mistake". Instead, he describes how he taped her up and dragged her to his car.
He told about her having wet clothing, him forcing her to remove all of them, and about keeping her underneath his bed with weights and storage boxes to keep her in place.
IMO, he's twisted enough to be boastful about every detail, in HIS words and from HIS perspective, of course.
Other killers who had child victims have talked. Dennis Rader was talking to John Douglas as late as 2013 in an interview about the crimes and he was already in prison, serving a life sentence without parole. I'm sure there are others who have talked about kidnapping, torturing, or killing children, but BTK is the one I recall as some of the talking he's done is fairly recent. ( His two youngest victims were a boy and girl from the Otero family murders in the 70's. One was 9, the other was 11 )
My conclusion is that he may or may not try to release any info to the press or public through whatever means are available if he's found guilty, which I believe he will be.
At this point in time, with what is known about how he talked and talked and talked to police already, he likely had a lot to say about the 88 days he held her captive before her remarkably brave escape.
What he doesn't know yet, probably, is that this part is being left off from criminal proceedings to spare Jayme from testifying via video or other means.
I know we all hope he stays quiet.
Respectfully to all, IMO.