You’ve made the right decision and will move forward from all of this.
He may be remorseful and very sad about this, but it doesn’t change the fact that he’s behaved in a way that made it wrong for you and your daughter to stay. He shouldn’t have ever taken his frustration and difficulty in adjusting out on a three year old and then followed up by giving you silent treatment. This just isn’t acceptable behaviour hence you’re where you are now with plans to separate and move into your rental.
A decent adult would have handled all of this differently accepting a period of adjustment, but not one involving unkindness and being cruel to a young child. But you know all of this yourself.
Thankfully he’s being reasonable about the financial implications going forward. But no doubt he’s also relieved that you’re making the decisions going forward even if he has sadness that your own relationship is now irreparable. He’s just not cut out for sharing his space and relationship with you plus your child full time and it’s shown right from the off.
Of course your feelings for him have changed and you’ve been brave and proactive in solving the issue. Yes it’s unfortunate and unpleasant at the moment but your rental is there, financially it will be ok and you can and will move forward. You’ve done remarkably well at recognising this isn’t going to change and work and have taken the bull by the horns to sort it. All credit to you.