Firstly, sending you lots of good wishes. It’s hard handing children over for contact at any age, but it must be really, really difficult when they are this young and still so dependent on you as mum, even more so because you are breast feeding.
To start with, I would see a solicitor, they often do a free 30 minute appointment and you will at least feel better understanding where you stand legally. This will also give you the confidence to say no. You have to put your child first. Not cave in to the demands of your ex. If you think 3 or 4 hours is the maximum time she can go right now without needing the option to be fed, then try that to begin with.
If you don’t agree with 8 hours and overnight when she is 1, say no. Put the onus on him to seek access. Let it cost him money to go through court etc. Just stick to your guns and keep her best interests at the top of your priorities. Children are most important, not the demands of their parents.
big hugs XX