Both of your points were the very first things I thought reading this.

A Sallen-Key filter is trivially easy to design if you work within certain constraints - a 2-pole Butterworth filter has the feedback capacitor exactly twice the value of the "second" capacitor to ground, if both resistors are the same value. If you pick 10kΩ for both resistors, 1nF for the feedback cap, and 470pF for the cap to ground, then you'll get pretty damn near a Butterworth response (Q of 0.707, maximally flat in the passband and then as fast a transition as possible to the stopband) at around 23kHz.

This is perfect.

And guess what? If you want to scale the cutoff, just scale the component values! If you use 15kΩ resistors you get 15kHz, if you use 22kΩ you get 10kHz, and so on. The minor error in Q will not be audible.