The relevant function is
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. There's no stat, I think - It's a hardcoded number plus
Main.sex.getNumberOfAdditionalOrgasms
, and that last part is local to a sex scene, and hence doesn't persist to saves.
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is how it's altered in an item's script; perhaps you can modify some script to apply it to your character every time a sex scene starts? If not that, I think you're out of luck unless you modify the code and recompile the game yourself.