You think you failed to find a new external position, but I think that's a self-fulfilling prophecy. Where are you located? Is relocation within the country out of the question? It's your life we're talking about, so be persistent.
If it helps, try to consider the incident as it struck me: you did top-notch work, really polished it up to offer your customers a quality of experience pretty much unparalleled in your market, and witnessed the disheartening collateral damage of having inspired the wholly uninspiring.
The off-brand stuff just never tastes quite right. If they were genuinely so immature about the confrontation, they're not going far. Keep on keepin' on.
Things work a little different for Facebook than they do for sites with more reasonable traffic. I've seen a few talks on YouTube where they speak about the challenges of scalability as they gradually hot swap legacy X or Y for their own in-house component Z.
See React/JSX and Flux, and the Haxl library. They go into detail about some of the problems and solutions that they've made public with respect to those projects, and they speak a lot about testing too in many of the posts. Worth checking out.
I was "diagnosed" with ADHD after filling out a 9-question Y/N survey, then left with a prescription. I was psyched to get what I asked for, namely the extended-release amphetamine Vyvanse which I had taken about a week prior and felt like a god among men, but these days I just wish they hadn't prescribed it (and that I hadn't asked for it, in that order).
A few years later now, my intuition is that psychostimulants prescribed and/or consumed with therapeutic intent really do not address the core problems that Shire (et al.) claim to be medicating, at least in my case. For me, it's evident by now that I lack the discipline that others have to put mind over matter and work through a task. When I take stimulants, I do feel like I'm working hard and getting my work done. When the deadline approaches, however, I'm left with virtually nothing to show after N weeks of what I really felt was good work in the moment.
I was more productive—quite a lot more—prior to experimenting with stimulants. It really feels like I'm doing better work when I'm on the drugs, but all I've done by the end of the day is think consistently and with huge enthusiasm about a lot of things vs. inspired bursts of real productivity in between my old day-to-day of playing video games. At this point, I think more about whether I'm high enough to begin working than I do about any pressing matter at hand. I don't recommend it, but I suppose it works for others. Sorry about the rant.
Don't let yourself fall victim to the false dichotomy of designer XOR developer; especially these days, there's no reason why you can't grind for a while and learn enough to make probably whatever you'd hope to make.
Plenty of great resources, and I can lend a hand if you need some help along the way. Just let me know.