Today exactly a month since we received the rfe, and today we sent them a reply.
Bf found his ex's petition for divorce with court registration stamp, which her lawyer filed to start divorce proceedings (it's good that bf doesn't throw away papers). This petition states that she lives and works in Poland and has no intention of returning to the US. Their divorce proceedings lasted almost 2 years..
On his behalf, bf wrote a small letter that they do not have contact and therefore we cannot provide other relevant information.
Now we can only hope and pray...