Welcome to the forum! Hopefully we can get you all set up.
1. Did you perhaps plug your surround speakers into the "Surround Back" speaker terminals on the Yamaha? If so, switch those to the "Surround" speaker terminals. The "Surround Back" are used with a 7.1 setup, and you're description made me think that maybe you'd done that. Several folks have had that same thing happen.
2. I'd have to dig into your owners manuals for the power issue, and I don't know what TV you have. You can check if there's a menu option on the TV for powering on over HDMI control in addition to powering off (which you say it is doing). I have this vague recollection of seeing a menu option on a TV that let you pick if you wanted to do one or both of those.
3. If audio works fine without the optical cable, then you don't need it.
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Often components will give you multiple options to make connections to make it easier to integrate with a variety of other systems, but you don't need to use all of them.