too early, but it'll take care of that leggy problem when you do. If no more transplants ahead, it's the best option to limit vertical height if that is a concern.
You got plenty of lip on the pots, so yes, you can definitely add some substrate too.
keep the light "right" and if it needs a prosthetic until it gets more robust, so bet it. prop it up one way or another. Don't go too far the other way with light intensity or the problems are arguably worse.