I have a very weak walnut tree (Mother Nature or a squirrel planted it). The limbs have been falling off easily soon after they're grown. Last year a storm took off the top 6 inches or so (the tree is around 8 ft tall now) and another limb is semi taking it's place. In a storm today, another limb (about 3/4 inch across where it meets tree) wripped off partially. I had to cut it loose before it stripped the bark off. It's very flimsy in a good wind. What kind of tree is stronger when it's young?
Re: Weak Tree
I think you just got yourself a bad, sickly tree. Saplings are usually much stronger and more flexible that what you describe, even for a hardwood like a walnut or oak. I'd yank that thing out and replace it.
What to replace it with would depend on what you want the tree for and the conditions and zone in which it's being grown. For shade I'm partial to maple or little leaf linden. Both grow fast and have a nice canopy.