shared residence does not mean shared care. shared residence conveys rights to both parents to say that the child has 2 parents if that makes sense?
shared residence as opposed to parental responsibilty conveys little extra in the way of legal rights but does convey to a child that it has two equal parents.
every child has a right to both parents but the practicalities of shared care for such a young child is not that good.
instead of lining the pockets of solicitors whose main aim is to do what is best for their client (ie you, the adult) and not what is best for the child (the legal obligations of solicitors is to the person who engages them, not to a 3rd party like a child), why don't you sit down with ex and talk?
shared residence will make little difference to you but a huge difference to dad and child. shared care is virtually unheard of for new borns, and as for no overnights for under 3's unless mum agrees, thats rubbish, my ex refused point blank for overnights even though I was my sons main carer before separation and I got shared res and 2 nights week and my son was 18 months old.
why not say to ex that to keep things amicable and out of court, no overnights till baby is older and settled but you will agree to shared res and contact during the day in between feeds (if you are going to breast feed) or for so many hours so many times per week (if you bottle feed). this way you can dictate when and for how long, appear to be very reasonable and co-operative and you control the environment where your baby is (and the new G/f has little to do with baby for quite some time).
work out, when you have come home and settled back in, when would be best for your ex to come see the baby (at your home or take out for walks) that suits your routine and gives you the time you will need to yourself. this way, if he disagrees and wants to go to court, your reasonableness will stick out like a sore thumb and show him to be unreasonable, but it is likely that his solicitor will tell him he will not get any better and tell him to accept. no court, no stress, no cafcass reports and officers sticking thier noses in right at the time you could do without all the stress of court/legal battles.
I am not overly good at writing letters but have written quite a few for mums as well as dads before, if you wish to see a solicitor go for it if it will put your mind at rest, otherwise I would be happy to write something for you to send (after you adjust it to suit your style of course!!)
the main thing I worry about especially when emotions are still strong is that the earlier you start legal actions, the more animosity and stress there will be.
you appear to be on reasonable terms at the moment, it would be the best thing possible for your child (and for you) to keep it that way if you can??
ps a court can order shared residence even if mum is vehemently opposed, in fact a lot of courts work on the basis of the more animosity and non co-operation there is between parents, the more likely they are to order a shared res order. my ex even made up lies about me being agressive and violent toward my son to stop a SR order it just made it more likely for me to get it though!!