Tongue flexing / bending when weight put on it

Agree, have a frame & axle shop inspect it. Doesn't sound good by your description and I don't know if you should even tow it off your property the way it is. There are a number of things that could cause this, including some that can be hard to see at first glance, esp. if you're not familiar with TTs. I seem to recall a forum member posting some photos of their A-frame that came clear off and he fabricated a new one, better than the original. Lippert's welding can be substandard too.