uhhh is it bad that i'd rather accept physical abuse over the sentidrien theory? anyway, that's something i've always wondered about, since adrien usually seems so tense/on edge around his father, but i figured it either doesn't happen (except 'chat blanc'), or it's not shown because of the nature of the show (a light-hearted cartoon). however, i think the problem with this theory is that adrien is a model, and as such any bruise will be immediately noticed by professionals in the field, or he might just not get modeling jobs. gabriel does seem to idolize his son's looks/career. is there a way your theory can work around this aspect of adrien's life?
Given that the physical abuse/Gabriel's anger management issues and all around bad parenting really don't come out of nowhere in the show and have been set up neatly over all seasons, and as long as you don't condone physical abuse irl, I'd say you're fine haha
Firstly, I think that Adrien's attitude vis à vis Gabriel in early seasons isn't necessarily a reflection of ongoing physical abuse, but rather of not knowing where they stand after Emilie's death (I can't remember if it was also said directly in the show, but Adrien says that Gabriel changed after she passed away in one of the Webisodes). That doesn't mean that there is no abuse going on, since there's definite emotional abuse the rest of the time; Gabriel manipulates Adrien and even others (e.g. Marinette in Chat Blanc) on several occasions, notably using preventing him from going to school as a threat. And after the Collector and his "anger fit" (since that's what Adrien thinks it was, and I think I said before that it can't have been something that was ooc of Gabriel, otherwise it probably would have made Adrien tick), Adrien could still be afraid of the damage Gabriel could do, even if it's not directly targeted at him.
Now to come back to actual physical abuse, I also did wonder about the model aspect when writing my previous post, and my conclusion was that Gabriel would be the type who takes his ring off (with a focus on the gesture) to slap Adrien's face (which in my mind is the "best" way to represent physical abuse, considering the context of the show) - it would be less likely to leave a long-term mark than keeping the ring on (which Gabriel would have thought of before hitting Adrien because of the image it would give out, and the scandal it could potentially cause). This would probably be followed by Gabriel apologising profusely, maybe saying something about being on edge lately, but not developing that point (or saying that it's hard without Emilie), that he really can't stand him standing up to him, but getting an icepack for Adrien's red cheek; I could see Adrien being good about it, apologising himself, but still being rightly emotionally scarred by the slap, to the point of not wanting it to happen again, hence Ephemeral.
The other possibility is Gabriel kept his ring, but struck Adrien somewhere that's concealed by his clothing, e.g. the top of his arms (since apart from that bathing suit photoshoot in Mr Pigeon 72, all of his photoshoots were dressed up), so a bruise wouldn't be visible, and Gabriel wouldn't have to stare at it every time he sees Adrien until it healed.