I don't know how to answer your questions regarding topping, etc... I did it and it worked, but I don't know the specifics.
Anyway, your plant looks really healthy, especially the leaves, but I agree with LIP that it's rather stretched.
Is it getting direct sunlight? Because, I grew a plant using natural sunlight once, and it worked great, but on the other hand, one time my friend found a plant growing wild underneath one huge tree, and that's "sunlight" but not direct, and it stretched really bad.