Oh he sooo would have 'accidentally' sent you that text on purpose!
Ah, Chonni... YOU GO, GIRL!!! Nope I don't think you were at all too harsh - he's put you through so much and it doesn't seem to get any better - good on you for standing up for yourself and for your little girl. You wouldn't want Mila thinking it's OK for a partner to treat her like that, so you're teaching her how to be strong now

Better to be partner-less than with one who causes you that much heartache and clearly doesn't treasure you like you deserve. I agree with those who said to get hold of citizen's advice and set some plans/decisions in writing - it's a bit of work at first, but it'll pay off with how it'll make arrangements clearer and so much easier for you.
Sorry I can't remember the name of the lady who'd replied who gets treated in a similar way... but you mentioned that your partner would go for custody if you left. I'm sorry to hear you're feeling so very stuck there. Just because he applies for custody, doesn't mean he'll win it. It's the Family Court's decision once it goes that far, and the Judge weighs up all the pros and cons - I don't know your situation, but your partner might be able to bully you into thinking that you wouldn't win it, but a Judge is used to people trying that stuff on, and they can usually see through it. There's always shared custody too - which usually gives mum's most of the time with the kids and dad's some too, but means you can have freedom from a dodgy relationship. Maybe following your heart on this and doing what you want to for you and your child could pay off in the end?