Oh didn't it say to review after the 12 weeks? That doesn't mean jump straight into full on alone access.
Chances are he would fuck up/let down etc during that time frame anyway from the sounds of it?
My view would be to avoid Court if at all possible - there would be a rubber stamped agreement for what it's worth but it is a fucking stressful and expensive experience. Let him drive down that road if he wants to.
Personally, I would have the solicitor write to him with the offer rather than nothing. It will be another piece of paper in your favour if you do end up in Court.
Also, I try to make decisions with DC imagination sitting on my shoulder as 16 year olds sometimes IFSWIM. It's an offer you have made officially. You have tried.
Hope that helps.