Benn act will still be in effect and Boris will have to ask for an extension anyway as a referendum would require it. This is the best we can hope for in my opinion. Labour go all in on remain, BP go all in no deal whilst trashing Boris, Boris goes "we have a deal, but NI aren't in it", very good chance in a referendum that remain will win out vs a deal that shafts the union. If remain does win then we will soon have a GE. BP will be splitting the tory vote a lot. Boris will have nothing to promise anyone, couldn't deliver Brexit, couldn't control his own party. May not be a Labour majority but it sure as hell won't be a Tory one either.
The hilarious thing would be to get an amendment through for a 2nd ref attached to Boris' exit deal and then watch as the ERG and Tories vote against their own EU exit plan due to the amendment, it could destroy them.