I like your story, it is sexy to hear it come from your point of view.
The toilet ads a nice touch, if you want to see it go bye bye forever. But personally I would like to hang on to it, at least for a while. Just to feel it in my hand, keeping it for myself would be a long lasting euphoric experience. And then to have it preserved in a jar to show off, would be unbelievable fun. If I met a penis in a jar, I would definitely want to meet the guy it came from.
More personal details about the fantasy. For me, he would be smooth and hairless. I wouldn't need to tie his hands, because he would be willing to give me what I want, but I could tie them just to keep them out of the way. It would be fun to take before and after pictures. Maybe less believable, blood would not be an issue, nothing more that a large band aid could fix. And most importantly, I would hold his penis in one hand, looking deep into his eyes as I chop it off with the other.
That's me