Pursue a German PhD with a Masters from the USA?
You can compute your prospective salary yourself: http://oeffentlicher-dienst.info/c/t/rechner/tv-l/allg?id=tv-l-2020 

Typically, TV-E13 but only 50% or 65% depending who funds your position. Whether that is enough is up to you and your wife. A career at the German university is a high risk gamble, and it take quite a while before you know whether you make it or not. If it does not work out, then you will have invested a lot of time in a career that did not work out.