You may feel taken for a fool, but no one will be laughing at you, whatever their feelings are, it won’t be amusement.
I understand about your self esteem, mine took a heck of a battering, (I was made to marry him, then left with his 'secret' children as well as my own) but you know your self esteem shouldn't be on the floor, wear it with pride, and if need be 'fake it till you make it'.
You are the decent one here, the one that accepted the other little girl and treated her decently, the one that does the hard work of bringing the children up, and you should be proud of yourself, you are clearly a good person, and in time it will be you your children are proud of.
What he wants is his problem; he can't have it both ways, right? They are your children, he's made himself a very part time dad indeed, and yes they often like to be seen as occasional fun parent while Mum does the hard work, but your children will see through it as they grow up.
If this was your daughter’s problems what would you advise her? It's what I ask myself when I need to know how to treat myself.
I don't know if some of the humiliation is to do with cultural expectations, breaking them, and then it not working out. (I'm from a culture with strong rules that made for a hard life) If it is, then it may be time to grow past cultural expectations and take what's good from your culture and leave behind what damages. Set your children the best example for the world they will enter, that you can, and divorce him, and take ownership and control of your life and future.