I'd be willing to bet that the optical connection on the back of the TV is an output. I can't think of any reason why a TV would have an optical input, but I know many new ones do have an output.
As for the HDMI audio settings... yep, you can adjust it on the PS3, going to the two different settings I mentioned.
Under Video Settings, you can select either "Linear PCM" or "Bitstream" for "BD/DVD Audio Output (HDMI)". To enable the surround sound to be carried from PS3 to TV to amp, I believe you'd need to change it to "Bitstream", so that the PS3 sends it as is (raw DD/DTS bistream) to the TV & the TV then sends it over optical - as is - to the amp.
Under Sound Settings, you get the choice of Optical or HDMI. If you choose Optical, you have various boxes you can tick for DD, DTS, AAC, LPCM etc. If you choose HDMI, you can select Automatic or Manual. If you select Manual, you get the same selection as if you selected Optical, & so can select DD & DTS instead of simply the Automatic choice of LPCM. Again, you'd need DD/DTS so it can be passed as is from PS3 > TV > amp.
[TV > amp cannot carry DD/DTS uncompressed as Linear PCM, as Optical does not have enough bandwidth for more than 2 channels using LPCM].
As I said before though, I don't know if this would actually work - I've not tried it myself as I just put up with changing the settings each time I switch from HDMI (for TV audio) to Optical (for amp audio) & vice versa. But I think it's worth a shot, & trying it out only involves hooking the TV to the amp via Optical & then quickly changing a couple of settings on the PS3.
