Float, sad to hear that not a good cheese.
I think the poor taste was more from the unwanted mold than from excessive rennet and that even while scraped before sealing, probably got baked into the cheese while aging, in which place it is probably too far gone to save, sorry. The question is what is the cause of the grey mold?
Can you give us more details? Milk type (fresh, pasteurized etc), starter culture, quality of cut curds vs ones pictured on this forum, how where did you dry it, etc etc?
I haven't personally made cheddar but will try to help where I can.