The azalea, I suspect is one of the North American native species, likely it is which ever one is native to the area around Mount St. Helens. Probably a deciduous azalea. They don't bud back as nicely as Satsuki, but they do back bud. Their growth will tend to be leggy, as they tend to keep most of their foliage at the ends of branches. Most deciduous azaleas have lightly to strongly fragrant flowers. Well worth growing, it may or might not submit to "bonsai techniques". But I would go ahead and try.
For the time of year, you don't have as many leaves as I would expect. Before you do anything get it growing better. They like at least a half day of morning sun, possibly more. Give it a year or two of growing without a lot of pruning to get a feel for its natural pattern. I've only had one or two, and they did not last in my care. I do keep Satsuki alive fairly well, have a couple over a decade in my care. So I do know the deciduous should be treated a little different.
My thought is that the hard pruning should only happen shortly before or just after flowering. When you prune back you will be leaving the tree leafless. You don't want to do this unless the tree is healthy, and not every year. So get it healthy first.
About the circling root, it looks like that root is supporting a good part of the bush. I would put off dealing with it for a couple years. When it is time to repot 2 or 3 years from now, I would apply a wrap of wire about an inch or two above the circling root, on the trunk. Make it moderately tight, to constrict the trunk, but not totally cut off flow of sap. When you repot, use a pot deep enough you can bury the wrapped area at least one to 2 inches. This will work like a slow version of air layering, actually sometimes called ground layering. But instead of peeling the bark and cambium off, you wrapped it with wire. The trunk should bulge above the wire wrap, and eventually sprout a new set of roots. Leave it at least 2 years before repotting. If it has sprouted a bunch of roots above the constricting wire, you can cut off the old root system. IT is not as quick as an air layer, but is has a higher success rate, and lower chance of loosing the entire tree. Air layering is not always 100% successful, this method is a bit safer.
But before anything else, grow it a year or two to try and get it more bushy.
Leo
