1) Logos should ALWAYS link home. There is no scenario in which a company logo should just link to anything but the main home page of the site. While it may make sense for YOUR site for the logo to link elsewhere, your user has been conditioned to expect logos to link to the home page based on the hundreds if not thousands of other web pages they've been to that use that feature. If you want the logo to link to the FAQ homepage, then redesign the log to include the company log AND have the word FAQ somewhere in that logo so that there is zero confusion as to where that link will take users. If you do that you can have the main site link right above that in small letters, the way the stack exchange and user experience logos are laid out on this page.
2) If the logo is a link to the main site, there should be no reason to have a link to the main site. I'd talk with whoever gave you that design spec and ask the reason for that.
3) You can use breadcrumbs after to show a link to the FAQ home page
Attached below, quick 30 second wireframe/sketch