I believe you can do that. You'll need to set up the IAP for the retail folio as well as the IAPs for the subscription durations before you create the viewer. I would create a dummy retail folio for testing in the sandbox.
I belive, you can not.
I tried to do so. Apple demanded the paid subscriptoin content to be present in review process.
I ended up to produce 2 folios.
You can not argue with Apple.