A couple of thoughts
As far as playing the USB, why not just put clips on a USB and bring it into your local store and try playing them on the TV?
As far as 2:35:1 resizing to 16:9, they won't resize perfectly to 16:9 unless you use the TV settings and expand the picture. Otherwise the 2.35:1 will have black bars along the top and bottom. So you have two choices: Use the 2.25:1 natively or resize them to lose the black bars. Keep in mind that 16:9 is an aspect ratio created for video, not film. Film can be shot in a variety of aspect ratios that don't always relate directly to video 16:9.
I don't use my TV audio-outs, so I can give you any good suggestion for that.