Does CBSubs include the ability to discount members who enter in a special promo code that we create?
There's currently no coupon system implemented, sorry. Best approach is to provide a plan that can only be seen with a direct URL. You could then give that direct URL to a specific set of users.
Can we control how long a promo code can be used and/or how many times it can be used?
Plans can have any duration you'd like from the pre-defined drop-down list of durations. Currently you can't limit a plan to a number of subscriptions, sorry. You can limit the number of renewals however, but this is not what you're needing.
Is there a report that will list who is using a promo code?
From backend you can see users have subscribed to, when, and much more.