I don't want to be too pushy in someone else's RP, so I'll make one last argument then stop. I haven't read the Case Files so I'm not too clear on the specifics, but whatever the first seven seals on Ron are they must already be broken/be easy to break by the time of the modern age if Gray, a normal albeit somewhat special human, is able to use it. And if Nasu isn't going to treat the specific conditions required to break the first seven seals as important (otherwise they would've been explained already), then why should we? Clearly the first seven aren't a matter of the utmost importance, so as long as we don't go past that there's no problem, no? ^^

As for the skill, that could be either ignored (say it was "locked" due to an incompatible/un-ideal summoning or Master) or we could just make something up. In a lot of Fate RPs I've been in before that was half the fun, since Nasu never explains like, anything.