I wish I could answer your question (our los are almost exactly the same age, btw
, but I'm slightly confused about this myself.
I'm not sure why you wouldn't be able to give formula at the same time as protein - I hope there's not a reason, as we've been doing it for ages
Charlie is still on 4 bottles a day, with extra bottles of water/juice in between. I have been gradually lessening the amount in his bottles, and started solids before milk a couple of weeks ago. I think I will soon replace his lunchtime bottle with juice, to make it 3 a day. We have lactose intolerance problems in our family, so I'm holding off on the milk for a while.
If it helps, your schedule looks fine to me. Are you giving him other sources of calcium, eg yoghurt/cheese/etc? That might be an idea if he's getting less formula.
Sorry I wasn't much help, I'm sure someone else will be more helpful.
Where are you from? I haven't seen you around the boards before. It's nice to meet someone with a lo the same age as ds