Let me preface my reply by saying wherever I might sound critical, I'm not criticizing you personally; rather, I'll be critical of a particular perspective. I'll start by first musing about the perspective you share with millions of other hobby growers, which was revealed when you said, "And it would be devastating to cut a significant part of the top when it is so healthy." The overwhelmingly large fraction of growers harbor the sense that any growth a plant puts on is sacred or automatically protected from removal. A grower might consider how long it took the plant to grow so large, not understand how to judicially bring the plant back in bounds by pruning or dividing/repotting, or simply looks at growth as a manifestation of his/her accomplishments. This mindset is so prevalent that most plants are left to do as they will until the grower realizes the plant is/has grown out of bounds to the degree that a major sacrifice in appearance or top mass needs to be made to bring the plant back to a structure that promises realization of the grower's goals insofar as what the plant should look like. The overall message is, if we start pinching and pruning well before we arrive at the point where a serious intervention is required, we never arrive at the intervention stage.
Just as life is largely a product of the decisions we make, what our trees will look like in several years depends on the actions we take today. Set aside our ability to keep trees healthy and you find how the tree was pruned/ pinched will have had the most influence on what it looks like as it grows.
"..... it is starting to lean even though it is right next to the window (facing East in California). Also, it has two branches going outward that looked in place when it was little but look weird (and obstruct the view) now." Your tree is leaning because cells away from the light source are elongated by one of the trees growth regulators, auxin. This causes the tree to bend toward the light. Or, it is bending because the trunk is not thick/strong enough to support all the top mass. Your best bet would be to summer the tree outdoors where it would respond with much greater enthusiasm (and thicken) due to increased light load and air movement. If you can't or don't want to do that, you'll need to keep supporting it mechanically, which certainly detracts from its rye appeal, or prune it back so it can support itself. You have noticed, I'm sure, that between 2 sticks of the same thickness but varying lengths, the longer stick is easier to bend than the shorter. The trunk of your tree is the same. My tree? I shorten it next June to the degree you can get rid of all the mechanical rigging that now supports the tree, and I would shorten it to about 2/3 of the ht at which you want to maintain the tree. Using the 2/3 suggestion is in anticipation of the room needed to develop a canopy. It will be exceedingly difficult to do that if you simply pinch the top (remove the growing tip of the stem/trunk). That will terminate extension of the trunk and force branching from 1 or more nodes immediately proximal to the pinch. I don't think you really want a bare 10 ft tall trunk with 2-3 branches at the top? Using the ultimate ht of a tree you want to maintain at 9 ft, you would reduce the ht to 6 ft (June) and let the branching start immediately below the 6 ft mark. That gives you 3 ft in which to develop the branches.
Should I cut the branches and just leave a single long stem? No, at least not if you're asking from the perspective of eye appeal or trunk strength. Think of the trunk as a river and the branches as streams entering the river. As the streams unite with the river, the river increases in size. The leaves and branches on the trunk provide the food (photosynthate/ sugar/ carbohydrates which adds files of cells that thicken lower order branches and the trunk. They provide strength, so removing them now would be counterproductive from the perspective of trunk strength. How do I stop it from leaning being that tall and thin? Cut it back and give it more light. Also, when you next repot you can change the planting angle so the top of the tree is centered over the point where the trunk leaves the soil. I find straight trunks a bit boring and movement in the trunk, curves/ bends very appealing to the eye. I finished pruning wiring this Ficus benjamina today:
This tree was once >8 ft tall. You can see the scar on the left where the trunk first starts to move to the right just above the soil line (not the orange/ brown scars I just carved yesterday) where it was chopped back to about 3" tall is nearly healed. It will look great when it starts to fill in. Should I cut the main stem to encourage branching? Covered. I prefer the tree shape but then I would have to move it away from the window to get more space, not sure the light will be enough. Summering outdoors and rotating the tree weekly will encourage much more growth and a thicker trunk. It will also help you develop a well branched canopy MUCH faster. It will also ensure the tree has plenty of reserve energy storedin roots and cambial tissues, which will assist it during the darker months of winter. And it would be devastating to cut a significant part of the top when it is so healthy. Calling on some 40 years experience manipulating Ficus and at least 100 other species of trees, I can say with certainty that the best time to do heavy work on tropical trees is when they are at the peak of health. When healthy, trees will take most of the indignities we force on them in stride. Doing the hard work (repotting/ hard pruning) when they're in trouble after severe decline is much like performing a serious operation on a person just hanging onto life by a thread. Tropical trees (grown outside of the tropical zone) are normally coming into their highest state of vitality and most robust period of growth when day length is longest. That occurs at the Summer Solstice. I regularly advise folks to be patient and make allowance for their trees' weakness during the fall/ winter/ early spring by avoiding hard pruning and full repots.
I don't know what camp you'll end up in, but if you have additional questions you think I might be able to answer, don't hesitate.
Al
Q
good advice
Q