Need Clarification on Roku Billing Services

• Can I still use any billing service if my channel is private?

As long as the channel is private you can pretty much do whatever you want I think. But the channel will never appear in the Roku Channel Store of course.

• Since users will have the ability to "rent" videos via one time transaction, do ALL of my videos need to be available within the Roku store?

I think the short answer here is: yes. However, if all the videos cost the same you could create a Roku Product that has the type of 'one-time purchase' and make the user purchase it before watching the content. How the consuming of this product is and what you do if the video is not finished and the user navigates back or something I'm not sure. I think that when the user purchases it through the Roku Store it immediately gets used as well, so the backend should set this video available for this user until the rental period ends. The frontend should be able to ask your backend if the rental period is over or not, and if it is: present the purchase option again. 

I need clarification on recurring billing concept if I delete the package from the store, Will it be a bill for the next month whoever purchased that package?