I know the devastation of losing someone you love and the heartache/heartbreak that comes with it, but I've been single now for many years and have found complete happiness being my own boss, so my advice (for what it's worth) will be coming from being a lot further down the line than you are now!
It's great that you and your ex are on speaking terms for the sake of your daughter and that needs to be maintained at all costs, whatever happens.
If he has left you and is keeping you dangling it's very unfair. I bet you don't know whether you are coming or going. Would you both be prepared to attend Relate for relationship counselling at all? That could be a first step.
However, he has chosen to leave you, for whatever his reasons, and I think you need to try and move on with your life as best as you can and make plans as a single parent. If he does decide that he wants to come back and you get back together that is always a decision you can make, but if he knows you are putting your life on hold for him to make his mind up then he has the comfort that he can keep you dangling as long as possible. Perhaps knowing that you are moving on without him, and coping with that, it will make him think more rationally about what his priorities are.
Now is the time for you to start doing things for you again. Kick start an old hobby or interest, join a new one, have time out with friends you've not caught up with for ages. If child care is an issue, have some girlfriends around your place for a night after your little one is in bed. A cheese and wine tasting night where each guest bought a specified cheese and a specified wine from a certain country was very popular with my friends. I hired 50 wine glasses for free from Tesco and we all tried reds, whites and rose we'd never tried before. I've recently had a girls pamper night and a local beautician came and did a 15 minute treatment on everyone for £5 each over the course of the evening and we all enjoyed a head massage or shoulder massage - the world is now your oyster and parenting aside you can make it as full or lonely as you want.
In my experience, a man finds his ex more appealing if they are getting on with life rather than being upset and pining for them. Then when they decide you are actually the person they want to be with you've decided they're NOT the person you want to be with after all and life is quite good and enjoyable as a single parent!
The one thing I would definitely NOT recommend is going out and meeting someone on the rebound (or to make him jealous and realise what he's missing). Have been guilty of that myself in the past and it only leads to more misery. Finding happiness in your own right as a single parent is the way forward, not finding a new bloke!