Just going to stop you right there, because I think you missed something rather critical: you only get 5 rolls by default. You don't have the total by then, you fail. You increase that by increasing Means. So given your later math of 10~ successes per roll? You don't finish by about 25 successes.
Given your supposed to get around that by acquiring Means, and not buying Larceny Charms (which have no link Sorcery in the slightest, why are you being incentivized heavily to buy this) I fully stand by my statement it breaks that system. Actually, given the whole 90% of your roll thing, a Supernal Larceny character can get ~21 sux per roll, which easily lets them push for Solar Ambition Workings at E1. The time scale is obscene (one year per interval), and its a +4 to difficulty on top of the usual Fineness difficulties, but it shifts it from 'haha no' to possible, which is so very much not the intent of the system, especially with fucking Larcerny.
So yeah, it breaks the system, in that the system no longer functions as intended, and in that it makes the optimal path to invest in Larceny. Which, for an Occult based system, counts as not functioning as intended.
*snip*
I think you can bring it most of the way in line by just saying that FSSA can only be applied to one interval of any extended roll, and not have to go way out of the way by rewriting either the charm or systems themselves. That way, you still get to 'cheat' a bit, but it doesn't snap Workings in half.