Silverfox,
Home theater bypass is very easy. You can send the left and right pre-outs from your receiver/processor to any analogue input on your two channel pre-amp. Just set the volume knob at a consistent place when using it for movies. If you preamp has a HT bypass use that setting as it will set a utility gain on the preamp.
the other option is to just wire in a switch like the one linked below. You can of course buy higher end switches.
https://www.amazon.com/Nobsound-Balanced-Converter-Audio-Selector/dp/B07D7P7366