I don't think many of the potential Labour voters will hold this against him as he clearly mentioned the reason. Moreover, Corbyn explicitly mentioned that he would love to vote for an election once the law is signed by the Queen. Also note that by abstaining instead of voting against the motion they can still make the argument that they're not against a general election.
Agreed. My point is the Tories will no doubt use this as ammunition against Corbyn for as long as there's no election date prior to 2022.
Corbyn can easily wait till the extension has been asked for before committing to a new election. But imho a new election will come and then we will see a unified hard Brexit side against a diverse choice of Brexit with a deal and remain. Considering the polls, I believe the hard Brexit will win, especially if they get the same media support as in the referendum. And to be honest I do not see why the parties and people supporting leave in the first place will be any less determined to push for the hard Brexit.
I'm assuming you don't live in the UK. I think you need to study British politics and voting habits more. Although I commented earlier that Labour and Tory MP's in safe seats shouldn't take it for granted, the simple fact is this: there are plenty of voters out there who will forever vote Labour or Tory regardless of the political issue of the day. Why do you think for example that the likes of UKIP have failed to make inroads into the UK Parliament despite previously getting a lot of votes in European elections? Why do you think that some constituencies have been safe Labour or Tory seats for over a century (e.g. my constituency has been Labour for over 100 years)?
Rightly or wrongly, some voters go as far as not bothering to vote if they don't want to vote for their traditional party for whatever reason but at the same time refuse to vote for their rivals or other parties.
You're also assuming there will be a Conservative/Brexit Party pact. Despite Farage saying he won't stand candidates in seats that have pro-hard Brexit Tory MP's/candidates, there is no guarantee the Tories will reciprocate and let the Brexit Party stand in some seats without a Tory candidate on the ballot paper. The Tories are large enough to not need to stand down candidates in some constituencies like the Greens have done in favour of other party candidates. If Boris Johnson decides a pact with the Brexit Party needs to be done, he's basically conceding there isn't enough support for the Tories and that will be a major comedown.
If we had a PR voting system, I'd be inclined to agree with you. However, for as long as it's first past the post, the best you can reasonably expect in some places is for incumbent parties in safe seats to retain them albeit marginally, with the Brexit Party potentially getting a few seats.
Finally, it's worth remembering that, rightly or wrongly, a lot of voters in the UK have used the European elections to voice their frustrations at the domestic incumbents. This is possibly one reason why British engagement in how the EU works has been lacking and why stories such as the EU being undemocratic etc. have been given a free pass and repeated verbatim for people to believe it as fact. It's why I don't think you'll see a surge of Brexit Party candidates elected to Westminster, though stranger things have happened.
Still, if you think the Brexit Party will do well, let's see their manifesto. Being a single issue party isn't going to sustain them in the long run as that's their raison d'etre.