Thank you for your kind words!
I see your point, however the issue with a free trial system is that it will probably be exploited. This site has been running for over 6 years now, and it wouldn't have been possible without the premium members. In addition to covering to cost of games, servers, software, hardware and work hours it also is an incentive to make sure the service is always improving, available, updated and relevant. Anyone buying a premium membership, especially a lifetime, is putting a lot of trust in the site and I want to make sure they always have an updated and reliable service.
A better solution might be to get 2 or 3 games with access to all conversion methods for free on sign-up, currently it's being looked at how to solve this or a similar solution technically.
Regarding a tutorial, the next thing coming up is a comprehensive written guide, probably somewhat integrated directly into the calculator. Videos are a bit quirky as they can't be updated easily, but the ones currently available are a bit outdated so new ones are definitely due.