Yes, there are single-country Interrail Passes that European residents can buy, as long as you don't reside in Germany, where you'll be visiting: http://www.interrail.eu/interrail-passes/one-country-pass/germany. The pass is flexible to use without much pre-planning. This is for people who have officially resided in Europe for the past 6 months or more.
Or, you may still get some advance-purchase discounts on German train tickets for specific dates and times, but not likely as cheap as when they first went on sale 6 weeks ago.
The Quer-durchs-Land Ticket works on slower trains after 9:00 a.m. For instance, you could take regional trains from Hamburg to Berlin, 4 hours with 1 connection (instead of the ICE that runs direct and takes 1h,45m).