I totally agree with the other posts. I just wanna add one thing.
It's a little hard to tell from the angle, but it looks like your feet are flared apart too much. Angle those feet in some more, no more of an angle than 45 degrees. I think that might help a little with your knees wobbling.
That and building hip strength along with your glutes and hams as others have mentioned already. Hip strength and stability for the knees can be built with wide stance work and single leg work.
A single movement that can build hip and P-chain strength would be sumo pin or block pulls from just below the knees. Just be sure to push those knees out and spread the floor. Sumo RDLs could work too.
If your upper back caving is due to more than just form and is a strength issue, they'll help with that too.