Tamsy is one hundred percent the type of person to be so in love with someone that he begins to feel genuine disgust because of how much you make him feel.
It kinda peeves me when people say that Tamsy would be ultra horrible to his partner, not because it's necessarily incorrect, but because I think it paints Tamsy's feelings as very one note. It presents Tamsy as someone who's horrible because he secretly hates his partner, and not because he's literally can't feel love in a normal/healthy way.
Even in a canon sense, I heavily view Tamsy as someone who would obsess over the person he loves. I have this image in my head of Tamsy wrestling with his feelings for you with the "true" version of himself. Tamsy knows he can't get close to you because of the risks, but he can't help but find himself drawn to you. He wants to know everything about you, the good, the bad, the ugly, the horrible. He wants to know what you love, what you hate, what makes you angry, what makes you sad. He gets so hyperfixated on you that he kinda forgets his own mission or purpose, he just wants to be enveloped by you. This doesn't mean there aren't the typical Tamsy behaviors however, he does push your buttons constantly, often disguised as teasing. It gets to a point where you often wonder if Tamsy actually likes you or if he's just making fun of you.
When Tamsy's feelings get so overwhelming, he genuinely starts to feel hatred and disgust, at you and at himself. He never thought it was possible to feel such strong attraction to someone else without some alter motive. He convinces himself that his desire for you is purely driven by his own goals, his greater purpose, before realizing that you're the only person he truly sees and truly sees him. This revelation fills him with so much anger, he hates not being in control. But whenever he's around you all of that just washes away and he hates it.
Tamsy is the type of person to look at you and genuinely this "god I love you so much I wanna kill you." His feelings are complicated, he's complicated guys—please do you get the vision...