I am in similar situation, and posed a similar question on another thread I created. I have asked one couple to be our joint sponsor, and my husband and I have a list of others we can ask also. Understandably, this is deeply personal information, with a fear mongering contract attached, so I got the "we will think about it and let you know." I am a teacher, so I need to leave by August of next year, after gaining a new contract in the US (I have been teaching internationally for 6 years now.
My plan is to hopefully gain a joint sponsor by the time we get to the NVC ( I am a December 23 filer), and eventually by the time my husband has his interview, I will have secured a new contract in the US during the prime hiring period of May/June.
Can you do something online? Work for a US based company online? I think by then you will have a enough paystubs to prove income AND take care of domicile issues at the same time.
Depending on the backlog in Japan, if you return to the US for a short time to get everything together you may not be separated from your wife for very long.