I don’t have much to add that hasn’t been said. I convert rust with Ospho, then coat with fluid film once or twice a year when I remember. My 40 has some rust but I don’t mind because it works for how I use it and this treatment seems to have paused any spread.
What I will add: don’t start stripping it apart without a rock solid plan in place. Unless I’m doing a full restore or something, I try to do things that won’t take me off the road more than a week or two. If you need to use a shop for something, make sure they know the timeline and know they’ll be expected to stick to it. So many projects end up in worse shape because they sat in the back (or outside!) while “quick insurance” jobs that paid better step in front.
Good luck, it looks pretty good to me from the pics.