Congrats, that’s exactly the ideal process for this kind of operation. I didn’t mention it at first because I mistakenly thought you understood that Pinegrow opens themes in PHP format and allows you to modify them directly.
Getting and cleaning up the HTML and all the resources (specific js, images, audio, videos, etc.) to then “rebuild” your theme with Pinegrow (using smart actions) was the right solution.
Thanks for your feedback.