You can apply different settings to each side of a spread by using master pages - though I'm not clear on why you would need to do that in this instance.

If you are working with a 11x17" paper, your procedure is already the best I know.

But things could be easier if you work with a spread of two 11x8,5" pages:

01. Create the document using "facing pages" option enabled.

02. Set inside margins to achieve the central gap (in your case, they are actually the same 0.5" in order to get the final 1" gutter).

03. In master page, use the command Layout > Create guides to set up your 6-column layout. Note the option to define guides inside margins only.

These two optional controls could also help your work:

04. If you want to edit the spread with both pages visible, disable "Allow document pages..." option in pages panel menu and drag page 2 to be together with page 1.

05. Use the File > Print booklet to finnish the work or make imposition in Acrobat with the excellent Quite Imposing plug-in.

You only need to create the guides on one side, then select all the guides (command-option-G), duplicate them (edit > duplicate) and drag the duplicates as a group to the other side. Not a huge timesaver, but it's a little faster.

There are scripts you can use to take care of this tedious type of work. You can find them in the usual places (eg Adobe Studio etc,)