(meaning he could well be stuck with Johnson's)

I am not sure about that. In order to get a deal done in three months then he has to work from something that exists already. I suspect he would start from May's deal, and negotiate on the Political Declaration section. We know Labour have had discussions in the past, and from the timing this would have been based on May's deal. We also know the EU indicated that some of Labour's proposed changes to the declaration would be acceptable in principle. Since May's deal is closer to what Labour want than Johnson's, I think it unlikely he would want to use Johnson's as the starting point.

The only other option which stands a chance of being agreed in three months takes Norway as a starting point, but that has not had the intense scrutiny that May's deal had, so I don't think it a likely basis.

I agree with all the rest of your comments, though, Steve.