I would say that's shitface's mod (rebalanced weapons): when I was running only Sanbox+ superpunch kills a brute in two hits, now that I'm running also rebalanced weapons it took me five/six hits to kill one of them; the same happens for destroying cars.
You have to change your shorcuts just like explained in this post: http://www.saintsrowmods.com/forum/threads/sandbox-for-srtt.1076/page-95#post-17851
(You haven't to read all the thread, but keep in mind that spend some minutes taking a look at the OP post would take you out of trouble 9/10 times)
and thats the reason why i have say that i havent read all^^
and thx for the answer

#EDIT how are the numpad numbers called? must i write NUMPAD_1 or what?
i want to use numpad number 1-3