Hey, not to worry, this audio, HDMI, hi-def, etc is getting very complicated
No, Connect the cable box video and audio as you proposed, video to TV and audio to receiver.
You can connect the bluray hidef DVD audio to the receiver two ways to try. Using the coax will pass the DD+ and/or perhaps some aspect of DTS. Check your bluray manual in the audio section to see if it will pass the TruHD as analog audio through the 5.1 analog output. If so, connect that 5.1(6RCA cables) to the receiver's 5.1 input used for SACD/DVD-a inputs as your receiver will handle those analog inputs. This way, with that 5.1 analog input to the receiver, you could get an uncompressed audio signal, high quality.