Help understand this weird wordplay/metaphor: 「あまりに肝を抜かれすぎて、お尻の穴から魂的な何かが漏れそうだ。」

Question

Context: MC has been isekai'd to another world in unconscious state, where nations are fighting for supremacy. A girl asked him to join her clan after brought him back to her house, but MC declined her proposal because he's not sure that he's ready to kill people (though he said that he understood that's just the rule of nature in his world too - in order to survive basically you have to kick people down).

Then the girl changed her proposal, asked him to become her husband, in exchange she will provide him housing, food, clothes. MC is so baffled by this, and this is his thought.

目が覚めてから、もう何度、度肝を抜かれただろう。あまりに肝を抜かれすぎて、お尻の穴から魂的な何かが漏れそうだ。
(my guess but not sure: "How many times have I been taken aback since I woke up? I’d been so shocked that something soulful was about to leak out of my butthole. ???)

Appreciates if anyone can help me understand the author's intention here.

More context:

Girl (seems to be the leader of her clan): 「衣食住を満たしてやる。その代わり───」
MC:「代わりに？」
Girl:「我の夫となれ」
Mc:「…………………へ？」
目が覚めてから、もう何度、度肝を抜かれただろう。あまりに肝を抜かれすぎて、お尻の穴から魂的な何かが漏れそうだ。
MC:「お、夫と申しますと、それはつまり旦那様的なものというか、綺麗に言えば生涯の伴侶と言いますか、そういうもののことです？」

Answer 1

Your literal translation seems already perfect.

It is a common metaphor that the soul is sucked out of a person who has been astounded, frightened or exhausted to death. As you can see in these pictures whose descriptions contain 魂が抜ける, the soul is usually drained through the mouth, so 口から魂(的な何か)が漏れそうだ would have been a more normal way of emphasizing MC's surprise. In your sentence, his soul is sucked out of his butthole instead of his mouth, but this is a joke on the author's part. The basic meaning remains the same.

Also, 度肝を抜かれる is an idiom meaning "to be astounded", and this 度肝 literally means "liver". In the past, it is believed that the liver was the center of one's spirit. So, although 度肝を抜かれる and 魂を抜かれる have different meanings in modern Japanese, they are quite similar when you look at the etymology.