He’s not thinking clearly right now unfortunately.
For protection against his brother plus the contract puts the seme at an advantage so it probably has to do with that as well
I understand the constraints of the contract, but I feel like this relationship offers nothing protection-wise. His grandfather does not disown him (in fact, he even encourages the relationship. which further upsets the brother), and the brother can still touch/harm the MC (that was evident right away when he fed the MC apples in chapter 10). The ML doesn't even notice/believe that the MC's life is in danger, despite having been almost killed multiple times (it wouldn't have been hard for the ML to find out about the multiple attempts on the MC's life). The ML is also extremely abusive mentally/emotionally and physically violent (I'm so tired of the 'rough sex' excuse when it's just abuse), and there's no care for the MC's general well-being. The ML is beyond indifferent to the MC, so it's easy for the brother to harm the MC (nothing is stopping him, and the ML has shown multiple times he wouldn't notice). And considering it's a life-and-death situation for the MC, I don't think his breaking the contract would really matter when the other option is death by choosing to stay there.
Not to be pessimistic (and please correct me if I'm wrong), but what's the point of continuing this fake relationship if it's not working? Like the brother is still making numerous attempts on the MC's life, and the ML is not offering any protection either (in fact, I would argue, he's even added additional harm to the MC physically and mentally). So I'm just confused where this story is going because wouldn't it be better to flee the country now? Or change just plans? I don't see any benefit to staying with the ML at this point.