wow, and oh.......I have just read thro the thread and am feeling very and for you........you have had a very tough day!
I too come from a very odd family set-up, along with an extraordinarily controling aunt, and as she bought me up, she unfortunately has more control over me that would be normal (I am getting help with it now, and I am finally becoming aware that I am the one allowing her to control me.....but I digress.....)
I actually think that your DH was made to feel by his toxic mother that not telling you was actually a good thing. with women like her, they are very very clever and practised at manipulating you into thinking that you would be doing your DP a favour by doing it her way. Just think, she may have told your DH that the family actually dont like you, and she feels sorry for you......you have no idea that there is a christening and that you have not been invited.
she may then have gone on and on about how he should be there with your DD (family duty etc), but he must keep it a secret so as not to hurt your feelings.
my aunt would and has tried this.....difference is I actually refused to listen to her, but only because I am lucky enough to have been accepted into a wonderful family that showed me that it was a far from normal as normal gets (IYGWIM). Had I been a weaker person, or maybe, a less confident person, I would not have been able to do that......altho that said, I am not strong enough as yet to really stand up to her (major issues just last week in fact), but I do still know it is not normal........something I think your DH is still not seeing.
he needs to get stronger, and I think you need to help him in this (which the way your are handling things right now shows that you are already doing). Having said that tho, I actually don;t think he is strong enough or brave enough to as yet stand up to her in the way you want, need and deserve. he is simply too scared (I would be, and I KNOW how awful my aunt is). The ONLY way I could do it is if I had 'protection' of my DH and MIL........and I am 35, not a child, but I still need 'back up'.
ask him what he is scared of, what could be the worst possible thing that could happen by him telling her........this is how my counceller is making me look at it. I have seen that the very worst thing (ie, her screaming at me and cutting me completely out of the family) is actually not that bad, as I have many wonderful friends (that I have chosen to spend time with, AND, most importantly, I have my DH and children and HIS family. I won;t be worse off, I would actually gain lots (as I would not have her stress!).
anyhoo.........I hope things resolve. I feel bad for you DH.....I can kind of see why he did it. It is in no way right what he did (and if my DH did it, he would have the 'kerrymum' treatemt), buthe was really realy stuck by the sound of it, and as it got closer and closer, so it got harder and harder for him to stand up and tell her how wrong she was.