The relationship between Marc and Myriam has nothing to do with a (RL-)BDSM relationship, it's a fantasy about an abusive son who exploits, rapes and dominates his mother. For players like me, it would be completely boring if it they would act like in a real life, consensual, trusting BDSM-relationship, even if they would do exactly the same sexual things.
That said, there are some flaws in his behaviour that dampen the fun (like him insisting that "she wants it too", which means his mindset is not in the "I don't care about her feelings" realm and he still needs to justify his actions for himself), but all in all it's interesting and there are not many games out there with this kind of pairing.
So I hope Zorlun will develop this path of abuse and misery further and not switch it into some kind of BDSM-done-right storyline.
Later in game there will be some BDSM kink, notably with Nubia and Charles, but yes, with Marc, that's not it, he's not a BDSM dom, is a cocky little asshole with a perverted mind due to the influence of his father, in that regard he can feel like a "victim" as his father gave him a broken vision of sex and how to treat women, which contrary to Anthony give him a little "door of exit" towards being redeemable.
But for now depending on choices, Marc can range from lost kid due to his father fucked up mind to real little shit that love to abuse others and notably Myriam, because he feel power rush from it.
Oh, I'm not saying that Marc's behavior is treated as healthy. I'm talking about certain other games, which I shall not name, where I've gotten in arguments with the developer who insisted there was no non-consensual content in their game and got very mad when I pointed out that the protagonist can (among other things) feel up girls while they're sleeping without getting their permission to do so in advance, as well as spying on them while they're bathing without permission. A scene doesn't have to be a violent strugglefuck to be noncon.
As stated just before, no, Marc's behavior is not healthy, he doesn't care for the pleasure of his partner and only validate hers when it happen because it feed his ego.
But as said also before, Marc's character is still redeemable, because he's still shaky in his conviction and most of his dominance is only bravado, he's not a real "dom" but try to show himself as one. For now he's exploring his sexuality by modeling his to the only real example he has, his father.
(Though here I'm only talking about one side of him, if the player chose to push him into the "dom" or "mischievous" side, if the player chose to push him into a "sub" or "normal", he's still lost on that front, but way more manageable and not too far gone in the corruption of his father.)
