I still feel the deck would run better if you added Black, specifically for Tortured Existence and Withered Wretch (which set up your own graveyard better than the claws). The T.E. allows you to split up your creature Qtys better and provide more silver-bulletesque choices.
And regarding the upkeep, I know you can alter your GY before your upkeep, but why bother? You'll be wasting the timing of a creature, and sometimes you simply won't be able to get it to work and will be stuck with an ugly upkeep cost. There are better creatures out there.