Sitemap and offsite page links

I need help with the offsite page plugin. I have Rapidweaver 6.4 and I do not use stacks.

The offsite links on the sitemap page give me a 403 forbidden page when I click on them.
They work fine in the normal site navigation, except I would like them to open in a new window, which is not happening even though I checked the box on the page General Settings to “Open in new window”. Help???

Under the Offsite options, where you add the offsite URL, would checking the box for “Use Redirect Page” help?