I m going to be blunt OP . You need to take a good hard look at how your partner is treating you , what his priorities are and how important you are to him.
You also need to stop trying to integrate yourself in your BF family. She’s not your MIL and even if she was, they are still not your family . If you and your BF split up ( which is a 50% chance ) you will probably never see them again .
So stop sending her videos and pictures, let your baby’s dad do that . I assume he has a Mobile phone , there’s no need for you to do this .
Dont see his family alone , only when he is there . Let him take baby to visit his family for the day at the weekend while you do something nice for yourself . If necessary , tell him you are going to visit a friend who is having a difficult time because her gran is unwell / she’s split with her BF / she’s worried about her job . TBH I’d say that at any given time there’s at least one of my friends who actually has some issue , so I’d just use that .
Then invest all that time and emotional energy you are wasting on his mum and his ex and his dog and put then into YOUR life . Your own friends and family , your own education or career .
don’t make any announcements or drama , just do a slow fade on your involvement . Be polite but distant - it’s not your circus and not your monkeys .
get back to work full time after your maternity leave . Your DP needs to learn to pull his weight in the house and with your child . And you need to keep your options open .
don’t use his family for childcare , only use yours or paid .
remember that right now you are losing income , pension contributions and career opportunities to protect HIS. But you have no claim on him if you split up . So wise up - you have a child to support for the next 20 years , you can’t afford to be self indulgent.