So, real adult talk here. He’s known her his whole life, and admits she didn’t start it like this. She got famous, “got a promotion,” had a ton of responsibility heaped on her, shows signs of severe stress (like biting her nails, lashing out emotionally, etc)... and yet the first time he ever appears to confront her about his dissatisfaction with their relationship is the day he’s already plotted ahead of time to leave her?
This is Alpha-Tier Beta going on here.
Hear me out. I’m not excusing her behavior. But someone in an adult relationship should have brought this up a long time ago, before it got this bad. No relationship is perfect, but you should at least try to work through rough spots as they come up, instead of letting them grow and grow until it’s too big to ever fix. Instead, he evidently avoided addressing the problems in their relationship until the day he literally ran away to take on a new identity.