The answers you get to this question are simply going to reflect the experiences and priorities of those who respond. At various times in my life, I'd have either told you "forget her; if you're passionate about your job that's what's important" or "quit the job; if she's special she's worth saving." Ignore it all. You're conflicted and the decision is going to be hard. Girlfriends will often be more demanding of your time than you want them to be, and more critical of time spent on your job than they should be. Conversely, employers will often push you to the point of neglecting your home life, to the detriment of your personal relationships. There's no one answer that's going to tell you what to do in this situation.

But I can offer some observations based on your post: If she's pissed that you had to pay taxes due to your down round, that's none of her business. If she's pissed that you're neglecting your relationship in favor of a questionable business, it is. If you're carrying anxiety home, you better have a significant stake in the company or you're jeopardizing your personal life for little gains. Some might even argue that jeopardizing your personal life for any monetary gains is a dumb idea. I prefer to stay somewhat agnostic on that one. If things are so bad that you're not having sex (but want to), something should change.

If I had to guess just based on what you've written, it sounds like the miserable part of your life is work, and if not for that, the relationship would be fine. Down round, anxiety going home with you, paying very real taxes on something of not-very-real value? These are work problems. If getting your girlfriend back is really a priority and your work situation is as bad as you make it out to be, one very viable answer is to quit your job, then call your girlfriend and say "I figured out that my work situation was the main impediment to having a good relationship with you. I'd rather have you than some shitty job, so I've quit. Please come back." If the job really was the problem, this is guaranteed to work.

Note, of course, that if the job wasn't the only problem, this won't work. But you've rid yourself of a shitty job and can move on. Personally, I feel like girlfriends are harder to come by than jobs, so take this whole thing with a grain of salt. :)