rowingdan

I agree, and in this case, it may look better that your wife went back to the US to re-establish domicile.
 
Good Luck!

Not needed.

Correct. However, I was looking into DCF as well and noticed you can potentially get approved if a change in employment happened for my wife which requires her to relocate to the U.S. on short notice. I was thinking that maybe her employer could write a statement for her to come back to the U.S. asap and then send this statement to the Frankfurt consulate for a request of DCF.
 
What do you think? Has anyone had experience with DCF?

Well, then it is a no brainer, mein Freund. Germany is the obvious answer.  

@rowingdan The I-485 fee is not refundable but it is cheaper than moving back to Germany. Up to you. USCIS typically approves requests to expedite EAD/AP if you have a job offer. In fact, sometimes they approve them without even asking for evidence. 
It seems to me like it would be cheaper to join forces financially with your wife and pursue AOS. Paying rent for 1 person is no different than paying rent for 2 people, unless I am missing something here. 

I understand your point. In our case however, we could live for a significantly cheaper rent at an apartment in Germany (my parents in Germany own a few apartments). The current rent here in California is only doable because my wife and I are sharing the apartment. She would not be able to carry the costs on her won once my personal funds run out.

I think one month is WAY too tight a timeline for your proposed plans, unfortunately. Until very recently, just getting a receipt notice was taking at least a month, not to mention biometrics. And you need biometrics before being able to expedite the EAD.
 
If she can keep her job and legally work in Germany for the 1-2 years consular processing would take, you should be fine.
 
I don't believe USCIS fees are refundable.

I believe OP is talking about typical i130-NVC-CR1 route not the DCF for consular processing. At present DCF is only allowed for exceptional situations anyway.

@rowingdan it really is up to you whether to pursue AOS or consular processing. If you choose AOS, you could always request to expedite your EAD/AP - specially if you have a job offer. You would need to wait until you get your biometrics appointment. Then, you would call, request to expedite and provide evidence of job offer. (It does not need to be a fancy job. It could be anything). If that fails, you could always reach out to your US Senator or Congress representative. 
 
It sounds like your wife is employed. That would make it easier for her to sponsor your I-864. By the way, federal loans are deferred until Sep 2021 - I think. She could always consolidate them to bring down her interest and payment. She could also switch to a more favorable payment plan. There are several. She could also ask for a deferment. 
 
I would set up a spreadsheet and compare $$$ for both routes. If you move back to Germany, you will face some start up costs. You would need to fly there - not cheap , get an apartment, get work permit for your wife. She would need to get a job unless she can work remotely. 
 
Those are all things to consider. If your goal is to live here, and you are already here, why not just stay here and make it work? 

I assumed OP's spouse is the USC? In that case, they could definitely AOS (as long as the J-1 doesn't have the 2 year home residency requirement).
 
OP, it is definitely up to you and your partner's priorities and possibilities. But you are correct in that the EADs are taking several months to be approved. You could always try to expedite them after biometrics, but it is not a given that you'll get the expedite approved, and that still might take months.
 
If you do consular processing, just be aware that you might potentially need a joint sponsor, since foreign income normally does not count to meet the minimum guidelines (unless it will continue after you move back to the US). If your spouse moves back before you interview and secures a job that meets the income guidelines, then you won't need a joint sponsor.
 
Good luck in this process, whatever you decide!