Okay, I can sympathize. Back when I was in research I had a lot more clout and income, but also no free time to write. At all. The job consumed my energy, and it was only after I (due to changing circumstances and a small mental break) I switched careers to a ‘grunt job’ that I had the opportunity to pursue my writing career.
Career… that’s the trouble here, ennit? Because writing is something that takes time. I’ve been working full time (and writing on the side) since 2010, but it was only 2018 I started making real money. Not enough to quit my job, mind you, but it helped. The thing that made me money (Fallen Hero) I had been working on since about 2014 on and off, and that’s the thing here.
You won’t make money immediately, even if you sell really well. A writing career builds up over time, since once it is out, it will keep selling. Once you publish your next thing, that will add to it. If you get well known enough that people might be interested in supporting a Patreon, that adds to it as well. But it is a gradual build.
I consider myself very lucky for a first time author with no following (English is my second language too). All my bookkeeping is in Swedish kronor, so they vary a bit depending on the dollar. If I assume an exchange rate of 8skr to the dollar, my 2018 income (published mid march) was around $11 250 (not counting any expenditures), in 2019 it was around $8 400 (no launch spike). 2020 might be similar from the looks. That’s not counting Patreon, which is too new to judge. What will happen when I publish my second book, we’ll see. It will be interesting.
My advice to you is to be smart. You have written fanfiction, and you obviously want to do this. You need to find time to write. Yes, I know it is hard, but you can’t quit your career and start from scratch. You need to get something out there first. Yes, it will probably take a few years, but writing ain’t fast. And if you really want to do this, you need to think in terms of decades, not months. Doing this will require sacrifices a lot more complex than just quitting your job, writing full time, and then maybe earn a little in two years. You need to plan for it, and from the sound of things, you’ve already started with the financial bits. House, car, no loans. Nice.
Now comes the hard part. Figuring out what part of your life you can cut down on. Yes, the obvious one is work, but you can’t quit yet. So the hard balance becomes cutting back on the space it occupies in your mind. Try to avoid bringing it home with you. Detach yourself, little by little. Remind yourself that this is temporary. A means to an end. Good money now so you can save up for the future. Sometimes it helps to have a goal that is not a career to make the actual work bearable.
The other part will be your social life. Yeah. Fun things, playing videogames, meeting up with friends, all those things. Can you skip anything there?
Being a writer means making tough choices. You won’t be a social butterfly. You won’t be able to play all the games, or see all the shows you used to. You need to get used to saying no to fun nights out, or the social functions you took for granted.
What you need to do is finish your first book (or interactive fiction). And yes, most writers do that while holding down a full time job, and in some cases also raising a family. It can be done. If you want it enough.