Hi there,
I originally "broke" my ankle in a very similar way to you by the sounds of it. Landing full weight with my foot not squarely planted on the floor. Ankle rolled and the ligament snapped the tip of the bone off. I couldnt possibly comment on the fact your doctor has said "the bone will probably scar into place" but I can speak of my own experience. My ligaments were intact and still attached to the piece of broken off bone and thats the way it stayed for over 10 years from the time of the original injury. I had a cast on for 6 weeks all those years ago and the bone definately did not "scar" back into position.
My surgeon recommendeed removeing this piece of loose bone due to the fact that it would be too tricky to re-attach. Ligament now held in place with bone anchors (which I can feel under my skin!!)
Its been around 7 months since my surgery. I had 2 physio sessions where I was shown stretching exercises and left to crack-on on my own. Ive been doing the exercises and the ankle was feeling fine - strong - no pain. I've been mountain biking heavily for the last 3 months and I have started to get a little soreness around the ankle but my surgeon said I should allow 6 months for full recovery. I have my last follow up consultation on Thursday, so Ill post again to let you know what is said.

I would definately ask your surgeon to make sure that the bone re-attaches itself - otherwise you will be in exactly the same situation as I was. An ankle injury not properly healed and progressively getting worse over time. Hopefully the cast will have held the bone in a position where it starts to heal itself.

I would use the walking boot. The one I had was not very restrictive and definately gave me confidence back when walking around again worrying if I was going to roll my ankle.

Let me know how you get on.