Pie - am also in a similar situation, so you have my sympathy. There is no great animosity between me and my daughter's father but she was 15 months old before he first saw her. I had to initiate ALL contact with him, feeling very humilited in the process. He does give me some maintenance now but it took 2 years to get anything from him. And what he does pay only pays for about 2 days of childcare per month. And it's never gone up in 2 1/2 years.
The situation is complicated by him living 200 miles away and being involved in another relationship with a woman to whom he has a further 2 children. He only told his partner about my daughter when she was 3 (she was conceived during a break in their relationship).
Before this, he was coming to see her about twice a year but things have now become a little more strained - last time he wouldn't even let me take a photo of my daughter with him because his partner is uncomfortable with that. He never telephones to see how she is.
Also, because of the original secrecy, I never felt I should pursue him through the CSA because I felt it was his responsiblity to inform his partner, not mine. Plus, I didn't want to create any impediment to him having any sort of relationship with his daughter.
For me, the money is secondary. I feel it is so important to appear positive about her father and totally honest - my daughter knows about her half-siblings and asks about them. She is half her father and any negative feelings you may have towards him will be picked up by her and directed at her - he's bad, I'm bad. Your daughter will work out the truth of the situation when she is older and realise who are the people who have had to do the real parenting. My daughter used to love telling me that she loves her dad more than me but this Christmas, for the first time, there was been a slight swing in favour!
I wish you all the best but children are not soft - they know what's important in the end. And, possibly, being a girl, she'll realise herself how much you, as her mother, have looked out for her happiness. And, if you can, forget about his tantrums. But, yes, seeking legal advice seems like a good idea.