Both options are just barely OK but should work:
As an economically non-active person, the standard is that you should not “become a burden on the social assistance system of the host Member State”. Therefore, the law does not include a predefined minimum and the amount should be decided based on the local costs of living. Not being eligible for welfare benefits should in any case be sufficient and I think that €15000 is enough for that in Germany. The best place to get definitive information for a given place/province would be the local Ausländerbehörde. Also beware: You need to show you have health insurance, so if you are not eligible for statutory cover through your work, you probably need to pay for a private insurance contract.
A part-time job is also enough, the standard is that it must be “genuine and effective”. IIRC, case law from the EU Court of Justice established that something like 10 or 12 hours per week is enough, but less than that could be more difficult. So here again you would be very close to the limit but it should work.
If you qualify, even as an economically non-active person, your wife can indeed work immediately without restriction.