Looking at the Railpass prices, you are better off with doing them, as your travel will be much cheaper. You might want to look at the prices for first class.

Will you just be travelling once or more over some time when you are back?

Because then the BC 50% could make sense - freedom to choose up until last minute and get 50% guaranteed. If you are just in a short time frame and do once

I did choose that over the possible more saving 25% with the special offerings because I hated to be locked onto a train.

And: txl/cdn/fra are hardly northern germany.