Can't speak too specifically to your experience Kyle but we've built a fair number of Craft sites over the last 3 or 4 years and never had issues keeping different environments in sync. Doing multi environment configs is pretty easy imo and we've always found it easy to manage and deploy from one repo. Of course, DB syncs are another matter but I'm not aware of any CMS that has a magic bullet for that problem.

I've been freelancing for over 20 years - and started on the web several years before that. My core is UX/UI design but with so many years of experience, I've become a very good front end dev who can build anything at a very high standard, using many of the current libraries like react and vue. I can even code a traditional backend (though only so-so compared to a traditional backend dev). That said, in my experience looking for UX/UI work, those other skills haven't really helped my land work. They can help once in a project for being able to better interface with other parts of the team - and I think they make me a better designer, but I've found they're haven't often landed me a job. So, for me, they're nice to haves... if you have the time, then I think getting into front end dev can make you a better designer. But to do it well enough that you could replace a good front end dev will take a fair bit of time and effort, so tread carefully. As others have mentioned, freelance brings a host of other responsibilities and isn't for everyone (I've seen a lot of people try it over the years and discover the unique pressures it brings don't suit them). If you can, try to take on some smaller freelance jobs while sticking to your day job... and build up a bit of a network and contact list. The grass always seems greener on the other side... take a couple smaller steps on that grass first before you over commit. =)