I think Syngin will stay with Tania unless and until it gets completely unbearable and she gives him his walking papers. He’s much too lazy to initiate anything and will follow the path of least resistance.
With regard to him ever finding a job or deciding on a career path, he’ll be waiting forever to find the perfect fit. I also think that his PTSD (which, in my opinion, is “over-diagnosed” by people who have never actually seen a bonafide mental health professional) is a convenient excuse. You’re just plain lazy, Syngin! I’d have more respect for you if you owned it.