A pseudoarthrosis can be quite painful. I don’t believe you at one time had a solid fusion (“12 month showed bony overgrowth”) as once a section is fused, the fusion does not change.
You had a cage (spacer) placed and it is not uncommon to have a lack of fusion, especially with a PEEK cage without autograph. This can be revised to a solid fusion but in my opinion, the graft used for a pseudoarthrosis should be an autograph (a small piece of bone from the side of your pelvis) as this has the absolute best rate of fusion. The surgery has to be meticulous as the graft has to fit perfectly against the interface with the vertebral endplate.
PT is fine but might not give you the relief you seek until you have a surgical revision. If PT does give you good relief and you have a “stable pseudoarthrosis”, you might not need surgery.