I'm also in the torn-hip-labrum club. It's the most frustrating injury I've ever had (played football at the D3 level - I was never a bjorks-level athlete), partially because it's difficult to diagnose without an MRI, partially because the symptoms come and go seemingly out of nowhere exactly as you described in point 2.
I took the surgery route, which included re-shaping the top of my femur (congenital defect left me with too much femoral neck for the hip joint, which led to the labrum tear that caused the impingement). It took several months to fully heal, but I was able to play two more seasons. My lateral movement never returned, but it was ish to begin with, so no big loss there. They told me a hip replacement in the future was virtually guaranteed, but I've been able to dodge it for 20 years so far.
Tying this back to Buxton, I completely understand how his issues can seemingly come and go and flare up in a really painful fashion, and I also get the frustration involved with an injury where it's tough to acutely pinpoint the cause. When I finally got the tear diagnosed with the MRI, a part of me was relieved to finally be able to point to something to be able to show my coaches I wasn't making things up. With the obvious caveat that not all impingements are created equally, I hope they give some real consideration to the surgical option. There's plenty of time for recovery, and the psychological benefits of eliminating these flare-ups are almost as important as the physical benefits. I would also strongly encourage the Twins to consider any future time spent in CF by Buxton to be a bonus from a roster planning standpoint