Very nice, finally a Soviet bomber!
Hopefully Pe-2 will follow someday.
It can potentially carry as much as a B-24.
Every good source that I've read on the TU-2 shows that 8300lbs simply won't fit to the aircraft. My guess is that the 8300lbs is a mistake by one author which then got copied over and over again to many "mainstream" "aircraft of WWII-books".
Here's a Soviet source which lists 1000kg as the "normal" and 3000kg as the maximum payload:
(It also mentions that the forward firing cannons have 150rpg.)