Apart from a user script (which most likely would be what be needed to interrupt the scroll), it takes me two quick scrolls to get to the bottom.
This could also be accomplished with End the key (on Mac Cmd and ↓ )
It is not a nice solution if you are not good quick scrolls, but it does the job for me.
So far all the user-scripts I have seen have tried to enhance this feature rather than disable it (e.g. FFixer). If you could work backwards from that script maybe you will figure out how to stop it.
It seems the call goes to
morestories.php via Ajax in the following function
function UIIntentionalStream and the scroll loader if you can find a user script that handles then hopefully that can push you in the right direction.