I have no idea if this is the right point for my speakers or not. I can manually change this..just not sure where to set it.
This setting isn't dependent on your subwoofer, but on your mains. You don't say what your main speakers are. Look them up, check their frequency response, and frequencies below the optimum for your mains should go to the subwoofer. This may be happening for you automatically in your receiver/processor. Better check your settings there too.
That error indicates you're trying to play a format your sound card doesn't like. But you give no info on your sound card, or how your system is hooked up. You have amps and a receiver or processor right? Hooked up to the computer how? The format might be one your sound card simply doesn't support, or it might be refusing to accept that format because an HDMI handshake with the receiver is rejecting it. No way to be sure with the sparse info you've provided.
We'd need full details on system hookup, sound card, audio settings in MC, and DSP Studio settings.