As far as when to repot, you might be able to do it now but I wouldn't wait much longer. The best time is in early spring when the buds begin to swell. If it were mine, I'd actually up-pot it into a wider nursery pot right now and let it grow another season to thicken up. This would allow you to also work on the branches this year. Then you'd be able to do your root work next spring with a proper re-potting.