Re no. 8
Even if it’s true that non-voters, should they be persuaded to vote, would vote in line with everyone else it isn’t true to say “Non voters don’t vote. And when they do, they vote rightwing.”
About a third of voters (more if you define the SNP as left wing) voted for either Labour or the Greens so it’s fair to assume that about a third of non-voters would be inclined to vote left wing. I don’t know how many would be inspired by Corbyn to actually get out and vote but it does represent quite a lot of potential voters.