It's not a misspelling, it's jargon. FWIW I prefer it and I think it's valuable to preserve in part because people who dig into it a bit learn about the history of the term and practice of putting publications (especially newspapers) together.
If the choice is betwixt overloading a morpheme and having two distinct I shall take the latter.
Right. Saying people outside the industry should feel free to use ‘lead’ instead of ‘lede’ is like saying people outside the tech business should feel free to talk about ‘kilobites’.
You can prefer one spelling over another, absolutely, but it's a bit too strong to say someone using the actual word "lead" is incorrect.