Hi there!
If you check out the `README.txt` you can find all the information you need for Patreon. As for downloaded video files, *.dcv files from R18 are not supported as that website is no longer running and their licence servers are long dead. In addition, the secrets they use to secure videos are different than DMM, so cross decryption would be impossible. The only alternatives you have is to re-purchase all your titles on DMM with the Download option, or subscribe to one of their premium channels which allow downloading videos.
No, you don’t need to purchase the non-Patreon release. We don’t openly advertise or publish this information so that we can avoid drawing unnecessary attention. Buying the app is simply the easiest, lowest-effort option for those who don’t want to do a bit of legwork. If you’re willing to reach out on Discord, connect with an existing member, or get a referral, you can obtain the same details without spending anything. We apologize for not being more direct, but this approach helps protect our community.