your assuming that max combat load and max fuel dont interefere with each other. It is common among aircraft of all sizes. Neither a Cessna 172 or a C-5 can carry full fuel and full payload without exceeding maximum weight.
Quite right Mr sprstdlyscottsmn.
The Su-35 BM are like its predesessors a Heavy Interceptor class fighter.
It could indeed mean that it can't take off with max weapons & Fuel weight, if so 11,500kg of internal fuel are no small feature so go figure.
But then again, it have an increased thrust regime..
Oh, and like the Tu-160, who allso cant take off with max fuel and weapon load..
Probably the Bear also, the Russkie like their long range option on many of their aircraft.
As for the Su-35 empty weight, it does come with new avionics, and possible some Composits.
Then again it also have TVC engine and more avionics systems witch will bring the empty weight up.
I think it will land somewhere on the 17000kg mark.