I wish I could help you. You are not the first person through trying to authenticate a painting. I think it is sad that such an authentication should cost so much. Many paintings might go undocumented and get lost in time.
Bobwrites a great blog and has a deep love for art - maybe he would have some ideas or be able to help you out if you don't get what you are looking for here.
Good luck and let us know what happened.