Your symptoms sound a bit like mine and I had decided that they were due to sacroilieitis. Maybe you should ask for a referral to a rheumatologist to check that possibility.
It seems odd, but there are several reports from people here of joint pains and aches soon after going on Remicade or Humira. It is almost as if the inflammation is shifted by treatment. The aches and pains should be treated by those drugs, not caused by them, so what is happening here?
Anyway, assuming that it is AVN:
1. No. Once it has progressed to the point where it is diagnosed, there is enough damage that limiting further damage is the best that can be hoped for. If the problem worsens, hip replacement/resurfacing is the only solution.
2. There are not many treatments - there is no current treatment that will restore the vessels and so pain control and limiting further wear and damage are the aims of treatment.
3. An xray will show any advanced problems and if that does not show anything, a bone scan should reveal any problem.
A quick reference: http://www.eorthopod.com/public/patient_education/6554/avascular_necrosis_of_the_hip.html