I don't know how he puts up with it, but I do know why. He was alone since he was a teen, and now his wife and in-laws are his only family. His dream has always been having a family and community. He'll bend over backwards to please his in-laws. It's unfortunate they treat him like that, and while his wife is sweet, she's a pushover and doesn't stand up for him.
Why the in-laws are like that? I don't know.
Gimp, Inkscape, and Scribus were terrible to use after using Adobe for years. Get Affinity suite instead and save yourself the rage and frustration. It's one-time payment license (not a subscription) and they have deals. I got the license for the three of them for $90. They are way closer to Adobe products and definitely worth the one-time cost.
I love the concept of open source, but you can only make so many compromises in quality and usability, especially if you're likelihood depends on it. Gimp, etc just aren't there.
(On the other end of the spectrum, Blender is so amazing I can still hardly believe it.)