Shared parenting doesn't necessarily equate to 50:50 time.
And while he may 'want' 3 days a week has he considered what is in your dd's best interests in asking for that? Question his as to why he thinks that is best and if you disagree then put your case to him and between you I'm sure you can find a good compromise.
My best guess is he is pushing for as much as he can, aiming high knowing he will probably have to give a little. Whereas if he went if for 1 day a week and then had to compromise... You get the idea.
Shared care can work, but he needs to put aside the 50/50 demand and work with you for the best needs of your child. Arrangements can and should be flexible as your child grows and needs change. What works now won't necessarily work when dd starts school for example.
Firstly can he actually accomodate 3 days a week? Does he work? Who has/would have dd when he was at work? IS he expecting his '3 days' to always include the weekends?? How is that fair on you if you do also work? Do you work? If not then maybe this arrangement would give you the chance to get a part time job, if you do then maybe it will help reduce your childcare costs... Does he realise that even with 3 days a week he would still be expected to pay you maintenace...
At the end of the day your dd has two parents who want to play a significant part in her life, even though they are no longer together. Money can't buy that. See if you can work together for your dd's sake.
Yes leaving your child (even with another parent) is incredibly hard, but your ex is going through the same as well. And in time you will get used to it and may even come to appreciate your own space and time.
There is no reason a child can't have two equally important parents, two homes, and two people who share the responsibility of caring for them. How you finally agree to arrange this is between you and your ex, but don't dismiss it out of hand just because you believe you are the more important parent to your child and your child only should have one home and one parent now. The world has changed a lot from the days of mum being the main carer while dad brings home the bacon as it were.
Look here www.spig.clara.net/
for help and advice on shared parenting arrangements.
Best wishes, it's a long road ahead but work together and your dd will be the one who benefits long term
Good luck
Gilly