Re: "Labor is pro-remain, right?"
"The will of the more or less half that wanted to leave or that of the more or less half who didn't?"
More not less. The vote was to leave. Its not even debatable its a total value consisting of a vote on 2 options to which one option gained over 50% of the vote as specified as the threshold for a result.
"The impasse of the last few years has been the consequence of the fact that you need a decisive majority for a change that fundamental"
Aka the rejection of democracy by those who live in a country supposedly under democratic rule. Democracy requiring those who lose the vote to accept the result.