Yes and no, GTPS.
You are absolutely right that the OP's dh should not be physical and/or agressive towards the OP, regardless of the situation.
However, as the thread has unfolded, it seems that the OP's dh is feeling completely undermined as a carer for his daughter. And little things the OP says suggest she doesn't have huge confidence in what he is doing e.g. he won't listen to her/do it her way/his way isn't working..
I agree with you that developmentally it's probably so much swings and roundabouts - now their dd wants mum, later in her life she might want dad - but I see hints here that this couple are going to pull eachother to pieces rather than see this and work as a team to just get the job done. Maybe he is the driving force in it, maybe not.. but I am conscious that usually these things are a dynamic and while I would in no way condone the type of bad behaviour demonstrated by the OPs partner, I suspect that there are two sides to this story.
You, for example, say "at the moment, [your LO] finds me more comforting. DP knows this and knows that DS adores him." There is a crucial foundation of trust here.. your DP trusts that you trust him as a father, you both understand that this is not a notch on your belt or a black mark in his book and - it seems - you both see this is only temporary and will evolve.
I think I am hearing something different from the OP.. I think that there is more of a value judgement attached to it.. and probably all sorts of other things underpinning this terrible dynamic. A lot of pain, either way.
Urgent counselling was suggested by someone and seems a good idea - but I would be cautious before demonising a man in this situation outright.. I think new babies do fundamentally rock new families to the core and involve huge renegotiation of the relationship and of individual identity, as well as exposing faultlines in the pre-existing relationship. One of the most 'sensitive' new men I know used to kick the door in frustration when his daughter wouldn't stop crying. I remember throwing a book across the room when I had put my ds down for the tenth time one night, got downstairs and into a cuddle with dh and the lights started to go on the monitor.. I think aspects of this situation were probably initially quite normal but the sleep deprivation/frustration and, in this case, one-upmanship is taking over and threatening to destroy this relationship if something doesn't occur to redress the balance ASAP.
Incidentally, my dh isn't doing something we talked about - and I don't tell him how to settle ds. I think partners sometimes have different ways of supporting infants to settle and I just don't think it helps at all when one partner is too quick with the 'helpful' 'oh but he doesn't like that..' or doesn't 'allow' the other partner settle a child for months yet then turns around and belittles them for not knowing what to do when they are finally given an opportunity.
Not saying that is what's happening here but I do think it's possibly more complex than at first meets the eye.
DH isn't trying what I normally do.. he is trying what he normally does, something I have always let him work out for himself.