Definitely get a counsellor so you have a place to offload this.
Stop worrying about things you can't change - he's going, that's that. Your dd will cope as long as she knows you always love her.
Be cautious about going all out for a 'good relationship' with her father. You'll be shat upon . That is, it will leave you, and your dd, vulnerable. Instead, think of you and her as a family unit. What are your boundaries now, in this new situation? Think about that, think about your needs, and review your boundaries frequently. Otherwise, everything will go his way.
Of course, you won't deliberately say mean things about her father. But beware of bulling him up too much, covering up for his failings. My dd was 4 when her father and I split up. I covered up for him, I wouldn't do it again. She split with him when she was 21 and still suffers from depression relating to having had to know him. A clean break would have been better, but that wasn't 'allowed' even then.
Get yourself a pile of cushions, including floor cushions. Beat shit out of them. Call them by his name and tell him what exactly he's done wrong. Do this a lot. I got that from a book by Dr Irene Kassorla. I've employed it well, over the years.
I think you're going to get much, much more angry. Especially when his new woman comes out of the woodwork. When her needs are put above those of your child. When, for example, she and daddy ensure they are on holiday abroad every year on dd's birthday, so he can't be involved in birthday celebrations. That one's a killer. Of course, your ex might not be a bastard. We can always hope.