I'm sorry you had such a stressful time with PND and now it seems your husband has become more controlling as the relationship has gone on. Too rapid weight loss isn't good for us and if exercise has gone beyond normal limits of a hobby then it's not surprising if his temperament has changed in the past year.
I see you mention your DD has been a poor sleeper which must affect you both. Moving house is yet another stress factor.
His relationship with food is starting to impact on you and your daughter. It is possible to become fixated on something to an unhealthy degree and act differently at home but still behave normally in other circumstances.
Pregnancy and looking after infants can make us emotionally, physically and financially vulnerable. If following your PND he started to suffer with depression or some kind of MH illness then he might not be able to recognise his own problems. He might very well convince himself you are the one with a problem.
Health visitor care continues until your child is five years old. Health visitors work closely with GPs. Have you described to your HV what he is like?
You refer to your inlaws, but do you have told your family what's happening? I would put them in the picture first.
I would consider having a break from each other, make arrangements to get away from him for at least a long weekend. Contact Women's Aid without fear of him finding out or interrupting.
Think long term and the kind of environment you want your little girl to be brought up in.
It may not come to complete separation but don't think you have to trundle on getting ever more unhappy. You have options.
Why does he think he would he get your daughter if you leave? You are her primary carer.
IF you get to a point where you can't see yourself staying with him then I would advise you to seek advice before you do anything and certainly before telling him you want to end the marriage. Visit CAB if there is one near you, go onto websites such as Moneysavingexpert.com and use their benefits calculator, or Shelter to see about where you might live.