Hey dude, I'll just comment quickly from a mastering perspective. I think you got it for the most part, and there's nothing wrong here. However, if I were mastering it, I'd do two things:
1. Pull back the mid trebble a bit. That 2k to 6k band is really easy to miss when you're going after everything, but I find that that area takes up a lot of space and, for me, is one of the most annoying things when I go to turn up a track and there's too much of that in there. Just a broad eq set at 3k or 4k for the center brought down by a db, if that, is all I'd add. You could accomplish the same thing with a very light application of some sort of distortion or saturation, especially tubes.
2. I'd aim for something a bit louder, even if it is ambient. Regardless of genre, I start with an aim for around the middle of the road of what most streaming services will take for loudness, which is -14 LUFS. If you're already there and you still want it louder, keep pushing it. As long as you're not clipping like crazy, you'll be fine. Just turn the output from your limiter down by at least a db to leave room for overages and conversion. If you have to push your limiter too hard and it's distorting, run a second one after the first. I try not to have one limiter remove more than a db from the audio, and I use Izotope's IRC IV on the cleanest settings. If you're using something a little less clean, you may want to be even gentler.
Hope that helps, you're really not far off from having a pro polished sound, it's just that last few percent is the hardest to get. But, with practice, you can get there