How to skip cut scenes

I've played the game and looked through the wiki, there is no use that I've seen for the miscellaneous items that you gather from loot chests and dead bodies. The names for everything is just filler, make the player feel a sense of pride when he picks up a Diamond or Smartphone. The only quest items you will gather would be herbs and leather, occasionally some other item that you can only get while performing the quest.

The game does not give you the direct oppurtunity to have multiple save files for one playthrough, so you will have to go to the "system settings" -> "memory units" -> "memory device holding your saves" on your xbox and then copy the savegame you want onto a different device (e.g. USB stick).
That way you have a backup if the savegame corrupts.
It is a lot of effort but the only way to do it without a modded xbox, sorry.

There are 3 missable things: The achievements "Unheard" and "Fully Inked", and the alternative ending. Everything else can be done after you played the story to its end, as you will still be on the islands.