you’re asking the wrong questions
I’m seeing a lot of speculation about how Stefan and Caroline can make it now that he’s human and she’s a vampire. There are many ways they can work around that. That’s not the real problem they’re facing.
The problem is that Stefan has no clue what he wants. Caroline has no clue what their lives could possibly be. Neither of them are saying what should be the fundamental building block of whatever life they can possibly have together: I love you. Caroline says she doesn’t want to throw everything away, but she doesn’t get into the why of the matter.
It remains a big problem with Stefan and Caroline. The two of them danced around each other for a very long time. When things get tough, they tend to back away from each other. It wasn’t long after Caroline agreed to marry Stefan that she was taking the ring off.
Outside of the hug when they reunited, they were not handsey. I’m not talking sexually. I’m taking about Stefan being seriously wounded with no magic healing blood to fix him and they weren’t grabbing onto each other for dear life. They lack of physicality between the two of them has been attributed to bad chemistry but I’m going to propose something different: it’s intention, at least to a degree.
Stefan and Caroline love each other, are attracted to one another, can see themselves being happy together - but they are not in love with each other, not like they were with Elena and Tyler, respectively.