I'm wondering if things could take a different direction.
The EU, by insisting on a backstop to protect Ireland and the GFA, are vastly increasing the chances of a no-deal which would significantly damage both. They know that, even if they don't admit it.
Now, let's say we get to 19th Oct. The best thing the EU could do would be to refuse an extension, thereby making our exit on 31st Oct certain. Written in law. "No ifs or buts". We. Are. Out. However - at the same time they agree a deal with Johnson (backstop or no backstop, or something new).
That deal gets put to Parliament and all those MPs who've been wailing and gnashing about a no-deal for so long simply MUST vote for the deal on the table or - and here's the twist - they are guaranteeing we we leave with no deal. Parliament has voted against no deal (twice I think?).
All Johnson needs to do is field a bill stating very simply that we are bound in law to leave on 31st Oct and the only remaining options therefore are to vote for the deal on the table, or to vote against it, which is a vote for a no deal outcome. Surely even the worst self-serving parasite in Parliament doing their best to hinder Brexit would realise they are trapped. How can they vote the nation into a no-deal after all this time wailing about the disaster it would be, and after telling us how wonderful the EU is - the EU who has placed them in this position by refusing an extension?
Just airing my thoughts. I'm not sure the EU could bring themselves to go along with it, although it would be a quick way of reaching a reasonable outcome for both sides and it'd be p*ssing hilarious to see some of the faces on the opposition benches.