Mike 700 …. It’s not up to Boris mathematically.
If BJ does what you say he might in your post, then what’s to stop the cross party opposition from calling a vote of no confidence and agreeing a fixed term Prime Minister from among their ranks. They will then have (in theory) until 2022 to either repeal article 50 or agree a suitable leave deal, which would be irrevocably signed and sealed with an impotent minority conservative party sat on the sidelines.
The idea of cross party opposition staying together over an extended period is problematical, but they might just be sufficiently united by their common hatred of Johnson, Cummings and the ERG group at least for long enough to get the job done.
Two party politics has shown itself to be so deeply flawed by both extreme ideology and personal ambition that we may have to get used to the idea of consensus politics beginning to fill an ugly divide. It’s time to return to the “broad church” style of government that most MP’s support, and return the extremists to their marginalised little cohorts.