My reading is that the UK's opposition parties were not willing to go for a Vote of No Confidence, and then a General Election, because they were afraid Boris would pull a fast one and reschedule the GE after October 31st. This would facilitate a subsequent Conservative victory (a large tranch of their opposition comes from the Brexit party which would be neutralised by the UK actually leaving).
If there is a majority for Boris' latest deal we will know if the HoC get to vote on it next week. If the EU grant the UK a further extension I doubt it will pass. And if the UK get a three month extension next week I think there will be a VONC and a GE shortly afterwards. At which, I would offer, the Conservative party will either loose many seats to the Brexit party or form an allegiance with them.
As far as a negative response from the UK populace. Yesterday arguably the largest ever demonstration took place in London which was pro-Remain. While the Leavers may enjoy ticking dislikes on the Daily Mail website they don't mobilise in numbers. (A few months ago Nigel Farage promoted a march for Brexit from Jarrow to London. It fizzeled out through lack of support.)
It looks highly unlikely there will be any vote on the principle of the deal ("MV4"). The big vote (Monday?) will instead be on the Parliamentary timetable, with the government seeking to get the Withdrawal Bill through the Commons this week and then the Lords at the weekend, in time for the next EU summit. If the government wins this timetabling vote, then Brexit will happen on 31 October under the proposed terms.
But it seems almost certain the government will lose this timetabling vote. At which point the EU will likely grant a flex-tension, as it would be impossible to pass the Withdrawal Bill by 31 October.
What happens then? Well there's almost certainly no majority for a second referendum. And there very likely looks like a majority for The Deal. But..! There is also quite probably a majority for a customs union amendment in the Political Declaration.
This outcome as law suits neither of the major parties, as Labour would have to vote for Brexit which gifts votes to the Lib Dems, and Conservatives have to vote for the customs union which gifts votes to The Brexit Party. So it's hard to see beyond there being a general election, after some more parliamentary jiggery pokery.
The protest this weekend while large, was not "arguably the largest ever demonstration in London", with the anti-Iraq War rally quite uncontroversially still the largest. Regardless, the importance you place on protest sizes versus democratic votes is quite a peculiar one. Because one thing that the Daily Mail demographic definitely do is vote.
If you are hoping that these voters will now flock into Nigel Farage's arms delivering the election to a Remain Alliance under Corbyn, latest events suggest you'll be disappointed. Farage has been roundly criticised by his supporters both online and elsewhere, as putting his ego ahead of Brexit. Arron Banks who bankrolled Farage for over a decade has come out for the Johnson Deal. And all the polls suggest the Leave voting coalition has hardened behind Johnson, who is now ahead of Corbyn as "Best PM" in every voting demographic (including the 18-24 age group), while the Remain vote in England and Wales has been bifurcated between Lib Dems and Labour.
Knowing this, it would be in Labour's interests to try and defer an election still further but it's almost certainly in the interests of the SNP and Lib Dems to help the Tories have one anyway. That said, don't rule out that the next three months sees no election and no further legislative progress for anything Brexit related. At which point Macron really may lose his patience.
But attempts to amend the deal is about a lot more than just what specific amendments state; it increases the odds of the deal being rejected.
