The song Sign of Evil is based on

Not convinced.

Don't think it's close

That's a bit like saying "The House is Rockin'" by Stevie Ray Vaughan is based on "Sweet Home Chicago" because both songs are 12 bar blues. There is a vague atmospheric similarity but the timing, drum lines and melody lines are quite different. Unless Bobby Prince has explicitly stated as such, any similarity is likely coincidental or at best it was unintentional inspiration.

You really think Romero gave Bobby this kind of music for inspiration?

That's not even close.

The song posted bears more of a passing resemblance to Mark Klem's Dreadnaught:

It's still way off though.