TBH thats pretty low-quality. Few things that jump out right away;
1. There is extensive background material officially that there were 10 Legions created originally. So, don't tie it back to the First Founding (cos thats set in stone, fluffwise), maybe a Second or later Founding (you'll also need to give their Legion of origin ie Ultramarines)
2. Instead of founder, I think you need to focus on a Chapter Master as the martyr in your narrative. Being a Successor Chapter, I would think its Chapter Master is a former Captain of one of the First Founding Legions (again, probably Ultramarines).
3. The name is annoying, change it to something else. Or even better, read the DA codex, it features several Successor Chapters which fit your 'redemption' theme.
4. As far as 'corrupted' SM go, here is the distinction; either they serve the Emperor (and therefore are not corrupted), or they serve Chaos (totally corrupted). Halfways are either renegades on the slippery slope to Chaos, or Chapters on penance Crusades.
I would seriously reccomend you re-read the Space Marines, Dark Angels and Chaos Space Marine codexes. They all have valuable official fluff which would help shape your idea from being totally left-field (its current incarnation) into something which does fit (like I said, DA successor Chapters fit your theme perfectly).