What Carl-E said above. Saving people from themselves sounds like a noble goal, but in practice it seldom works out for either the prospective rescuer or rescuee. Only Dora can choose to "save herself" here, and if both she and Marten are in a place to resume their relationship after she's saved herself, so much the better. But before then, it's best for both that they go their separate ways for now.
I never condoned nor suggested saving her. But he
can be there for her. It's her journey to take but he could be alongside her at the very least. This is the sort of thing you work out together. You don't just pack up your shit and bail.
Before we were married, my wife and I reached a point where we were starting to fight, tensions were rising; it seemed like we were on the verge of breaking up. But instead of doing the easy thing, we talked. We talked a lot. We opened up, we confessed, confided, we opened our minds, and our opinions, and our hearts. And hoo boy, were there some fights and some very uncomfortable conversations. We talked to others, sought help when we needed it, and overcame it. And from that, we were married a year or two later and couldn't be happier.
What Dora and Marten are doing is stupid and foolish. She broke up with him. He's going to find someone else. He's not going to just wait for her to get better, and then everything will be rainbows and unicorns. People either grow together, or they grow apart. Broken up like this? They will grow apart. Change and evolve separately from one another, instead of symbiotically.
So if Dora thinks that she can get some therapy and then come back, that everything will be perfectly fine and she can date Marten again, she's in for a very rude awakening. Dora took the easy, disturbingly naive and cowardly way out, and Marten let her.
She's the one that jumped him like a lioness on a lone gazelle. How is she going to feel seeing him with someone else? Knowing the first, perfect, decent guy that she dated -- the guy that truly loved and cared for her -- is loving and caring for some other girl? If we thought Faye had a hard time of it? Heh.
As for his mother's behavior, I've given up trying to figure out her angle. Whatever it is, it doesn't seem to be helping him very much.