Unfortunately, what you are wanting to do is not really possible, at least not with just the tv and speakers.
The only output connections your tv would support are all digital. That is an encoded audio signal which has no volume level associated with it. Only analog signals are variable and can be adjusted in this manner.
What you'd need to do here is run the signals through a preamp/processor system that has line level outputs which could go to the speakers. This would act as an intermediary device to allow volume control by remote.
Here is an option for that which I'd suggest: http://amzn.to/2vbJpkv
Run the optical out of the tv to the optical inputs on this stereo unit, then connect the red/white from your speakers to the speaker out ports on the marantz. The volume control for the marantz will adjust the volume to the speakers and you should be able to program your cable/satellite remote to operate this volume as well.
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