Hi OP. Glad you are in a safe place with your mum. So, so sorry for all of it.
I've been thinking about you constantly and I'm sure lots of others have too. It's downright noble of you to post on here and give an update when all this is going on for you. It shows what a lovely person you are that you have done this.
You didn't need any more evidence but the 'I'm sorry' text says it all. You didn't get it wrong.
Comfort yourself with how well you have handled things. How ghastly the fear and panic must have been for your husband when he realised you'd got the phone and had rumbled him and his sordid little secret, panic that made him ring you up 'to check you were OK' as Vander predicted. Then arriving home to find you and his baby gone.
It's a pyrrhic victory of course because none of this is what you wanted, but I hope you take some strength from it in the days to come. You haven't let him off the hook or been a chump or a mug. You didn't swallow any lies, let him convince you of what you'd want to believe, or expose yourself to him trying to win you round. You've behaved with great strength and dignity.
Your husband will have a terrible Easter weekend with plenty of time and space to reflect on how badly he's fucked up his life and fatherhood. The OW will be no comfort - whatever she can offer him will seem shallow and empty and meaningless in the face of what he's lost. Nothing less than he deserves.
Stay where you are - in a safe place - and stay aloof. Your instinct to do this is very wise, hopefully he will feel too much shame to contact you when you are with your mum. Take strength from your baby (how I envy you a three month old daughter, my dd are much older now, a baby that age is so gorgeous). And hold on to the fact that, irrespective of him, you need to enjoy this time with your baby. It's all yours.
Don't beat yourself up when the adrenaline runs out and you fall apart, just stay in an atmosphere of support.
Cwtchy, read your thread at the time and you've also done inspiringly well and it's great of you to offer your support. Best wishes and strength to you both. xx