A few things to consider:
- Some of the Alt breweries are using things like co2 extract for bittering additions (Schumacher, for example). You can certainly go that route and get great results.
- You don’t necessarily need to choose between 15% AA Magnum (or Hercules, another popular high AA hop in Germany) and 2% AA hops–You can go with something like German Perle or Northern Brewer. Those are closer to 5.5-8.5% AA and are plenty often used in Germany as bittering hops (especially Perle, even as dual use, and particularly in Franconia).
- Given the low AA, I’m guessing your hops are probably 2023 as well. That was a horrible year for German hops. 2024 was far better. I’d consider updating to 2024 hops, and the better quality/higher AA of those nobles will really show in your final beer.