I was really iffy about what to do when it was time to upgrade cage size for my cham, but I chose to get a wire shelf from home depot and make a free range on that and I'm really glad I went with that option. I don't know if where you'll be living and putting the lizard will allow for such but...
my panther is about the same age and a little while back I took him out and his two back legs were really shaky as well. I had never noticed this before and figured it was the same problem. I now make sure his cage stays by an open window (temperatures permitting) and the problem went away.
If there is a local plant nursery near by, such as Pike, I would go check it out. They would likely carry stronger umbrella plants than yours. Umbrella plants that were older and had stronger branches. You could probably get one of those for around $50.