Nice article! I'd highly recommend this article to any other adult beginners out there!
I'm in much the same situation as you - Adult with kids, watched Queens Gambit in February this year, decided to have a go (having only ever played a few games here and there with my Dad as a kid), got hooked immediately and have developed a bit of an obsession haha. I've had very much similar experiences to you in terms of learning too, and have reached many of the same conclusions about effective learning.
The ones that stood out were
- wasting time on tactics puzzles that are really above my level, the end game stuff ( for some reason I just find the thought of it boring and I can't bring myself to study it haha),
- the ego and losing (once I convinced my self to embrace the losses as great learning experiences it really helped me). In fact that's pretty much the reason I started playing on this site (as I mostly play on that other well known free site), but I got so uptight about my rating that I couldn't relax and play well. So I started playing here for a place to play where I didn't care at all about the rating (and play my 'real' games on the other site haha), and just to play on my lunch break or something when I couldn't give it my full concentration. It was actually realizing that the rating doesn't really matter that paradoxically has helped me to start rising in the ratings again after plateauing.
-I've also had plenty of success learning the basics of a few openings, just as you have.
Not sure if we can post other websites here, but the only 'book' I have read so far is the free one on chesstactics.org. I think this was so helpful not only because it explains all the ideas in plain English, but because you are forced to calculate and visualise the moves in your head (i.e. its not an interactive board like most websites offer). I've really noticed my calculation skills take off as I've got through more and more of this book. I'd highly recommend it to all beginners. I've got 'Logical chess move by move' lined up next when I finish with that one.
I wrote a little article about my experience in chess over my first six months of play as a 29 year old adult beginner. Hopefully some new players can gain some helpful insights and avoid the mistakes I have made. Enjoy.
https://www.chess.com/blog/TheOnoZone/the-adult-beginner-diary-my-first-six-months-in-chess