Could you also add your thoughts on whether you think a B1 level is a sensible requirement for permanent residence in any country?
Because that's what the post seems to boil down to, but you haven't opined on it (other than refusing to learn B1, which implies the answer somewhat).
B1 by the way is considered doable for a consistent parttime learner in 9 months, and 1-2 years for someone doing weekend studying. That's an average.
For a studious family with higher educational background making 200k a year (this is significantly above average in Germany), you've got both the IQ and the capital for tutoring to do better than average.
Seems like a sensible, useful, necessary and practical bar to set for permanent residence, to me.