Esthetically, there should be little difference between the appearance of a twin-trunk and single trunk compositions. If the grower has the skills to pull it off, well-grown trees of either type will look very much the same, except for the fact one will have 2 trunks. Leave all the foliage on the tree for now. The small branches & leaves that grow from the lower trunk are fattening/strengthening the trunk and can be removed any time. They help to add a graceful taper to the trunk thickness, which is very pleasing to the eye and helps give the illusion of greater age. When the tree is about 2/3 - 3/4 the height at which you would like to maintain it, is when you might start removing lower branches and begin to work on the ramification (branch and leaf density) of the canopy. So, until the tree is getting close to the ht at which you'd like it to remain, your primary focus is best directed at just growing the tree well, and perhaps some gentle guidance in keeping the trunk straight or developing some gentle movement in it if you prefer. Branches will begin to form on their own in due time, but they can be forced to grow by pruning the growing ends of branches. Keep in mind that once you cut off the growing tip of your stem, it will never elongate further - you'll need to train another branch to vertical, or wait for the tree to develop its own leader. The later, waiting for the tree to develop a new leader, isn't recommended as the tree will seldom produce a new form pleasing to the eye once you terminate the leader, w/o some intervention on your part, that is. Al

If it were mine and I wanted it pretty much the way it is now, single stem with a bushy top, I would cut it back below the branches on each prong of the 'trident'. Put it outside in partial shade for a couple weeks to acclimate, and then move to full sun. Ficus back bud easily, and full sun will encourage this. Once new growth is under way, move into part shade so as not to produce sun leaves, which will not like being moved into a relatively dark house for winter. Ficus are known to drop their leaves if a shadow passes over them lol. If you want a bushy plant that branches near the soil line, you can cut the main stem to 6-12 inches, and proceed as above. There is a chance, however slight, that the plant will not like being chopped on and turn up it's toes, but I think it's a chance worth taking considering the state the plant is in now.

It's not losing leaves due to pot size. It's light related or other cultural factors. Ficus trees do not go dormant in the winter. They grow all year, but usually slow down a bit during the winter. Yes it does look like it needs to be repotted, but you can wait until June without issue. id get it closer to the window. As in right up in front of it.

I forgot to mention, I just read in an old post that pale yellow growth could be caused by growing in cold weather, maybe this is the same thing and I shouldn't worry until summer?