"So, questions: I'm trying to make the old man come out as crazy, and possibly not the nice-sort of crazy. I want readers to see him as a stark raving lunatic-who may or may not understand what the hell he's doing. I've never written this sort of character before (and it shows)."

Don't change a thing. Really, this left me feeling nauseous and weirded out, while I usually regard written things with a morbid fascination.
The guy was indeed rather crazy and it showed. I felt sorry for Helen, though. She seemed very out-of-place and forced into the carnage.
To reiterate Phineas: it's very well written. Struck the right balance between madness and reality.