Bit worried about you Rob. I know that you are predisposed to running through injury and your Crohn's has meant that you have developed a high tolerance to discomfort and the determination not to let anything stop you but I wonder if a marathon is pushing it too far?
I've started tentatively running again and have done a 9m fell run but my ankle is definitely still not up to long distances and I am suffering from my ankle brace the same as you. I had to take it off due to the blisters on my last run but during yoga last night, it became clear just how much less flexibility and strength I have in my injured ankle. I think Cyclops is right...I was told to do loads of glute exercises, squats etc and was really good about doing them until I started feeling better and cycling loads and now I've dropped off with my physio exercises but I'm going to get back in to them asap. I'm impatient to be back running long distances because I have had a great year with LDWA events and a good three peaks but that was before the sprain...
...looks like its a slow recovery for me but I am hoping that it will be a longterm one (well, until the next injury!).