Nondisp webr b fx with soft tissue injury in jnt caps+partly torn aftl delt no union orif+bone graft how in terms of severity would this be described?

Nonunion . Because of the nonunion, that is the focus of the fracture healing complication. The fracture type is relatively minor compared to the concerning nonunion.
Not terribly severe. A non displaced weber b fracture is not very severe. I'm not sure why an MRI was ordered to evaluate. Many times when we order an mri, because they are so sensitive, we don't always know how to interpret there results. Everyone with your injury could have the same soft tissue injury, but we don't know because we don't order mris on many weber b ankle fractures.