LOL...I never thought of that before.
Well, as a child, I took it to mean the same as "knock me down with a feather!" He was so struck weak by the surprise of what he had learned that the slightest thing, or breeze, would knock him off his feet.
He wants her to give him oral sex (a blow job).
it's not what you're thinking dirty minded one.
Actually, it is what he's thinking if he was thinking dirty.
There's an old song called "The Sailor's Hornpipe" which includes the line "Yo, ho, blow the man down"...sailors would spend long days at sea and return to port looking for sex. The writer was clever enough to get the line included in the cartoon because it wasn't on a list of forbidden words & phrases.
Popeye, for got to put the comma - "Well blow me away, Olive." Now, whatever your imaginations picks out from that is entirely up to your imagination.