I am not over 30, but I can tell you I got a divorce from my incredibly unhappy marriage, after 6 years also. I stayed with him because I was convinced that no one could "put up" with me, or love me for all of my weird quirks and my sometimes abrasive personality. I can be a sweetheart but I am also sarcastic in my humor, and he had me convinced no one else would put up with it much less APPRECIATE it....
Leaving him was tough. I landed in the hospital multiple times for anxiety attacks and it was HARD. But if I went back in time I'd do it all over again, with the knowledge that there WAS someone out there who found every single thing about me adorable, can throw my sarcastic comments RIGHT BACK AT ME and spar in that way (which is all in good fun for us, since we have the same sarcastic sense of humor) and I love how happy my NEW hubby has made me.
He was also in the same situation, he stayed with someone for several years because he didn't think he could find someone better, someone he really clicked with and who made him happy. I love all his weird personality traits and I think without them, he'd be super boring!
So that goes to show, settling is NOT the way, and you deserve happiness!
No matter what you choose, I wish you all the luck and love and support! But just know that if you aren't happy, there is someone out there who will make you happy!