2. No one in a constituency tje majority of the voters of which voted leave would have the heart to campaign to remain. Since most constituencies voted leave, most constituencies will field only leave candidates from all parties.
The election campaign will probably be more like two parallel campaigns, one in the majority leave constituencies and one in the majority remain ones.
3. Since all parties will probably field leave candidates in the 'leave' constituencies, the new Parliament will probably be majority leave, triggering Article 50, giving it two years to negotiate a Brexit to then present the agreement, if any, to a new referendum.
How people vote then will depend on the state of affairs and any proposed agreement between the UK and the EU at that time. Beyond that, I find it hard to predict how the people would vote in that referendum. While this was the leave the EU referendum, the next will be a remain in the EU or accept the new UK-EU agreement-if-there-is-one referendum.
Where I could see a major storm brewing would be the following.
The EU decides to play hardball, won't budge on migration policy to have access to the European market, and so the UK government, also not willing to budge on migration policy, calls a referendum to stay in the EU or accept a CETA-style agreement (meaning a comparatively closed border but with the UK controlling migration).
The voters, knowing that a CETA-style agreement would hurt their economy but feeling blackmailed by the EU, vote to accept the CETA-style agreement as their way to show the EU the proverbial finger.
This hurts the EU and especially the UK economies as the UK closes the border to migration and both sides limit trade.
The UK is thrown in deep recession, the EU in minor recession, each side feels bitter towards the other, and we begin to see a further rise of nationalism in Europe anew.
That's a scary scenario, though I hope a brighter scenario emerges instead.