Some thoughts on this topic.
2. The J-15T may have better range/payload performance than the J-35 with external weapons loadout.
I think it is a given that a heavy fighter would have far greater range and load than an aircraft with medium class engines designed for stealth. Stealth and performance planforms do not always match up.
But on top of that, the Flanker airframe has famously immense load and fuel capacity. The Navy needs a multi-role fighter like the J-15 for the foreseeable future just like the USN still flies the F/A-18 variants. It might cede the CAP and A2A roles in missions to the J-35 but certainly not the strike roles.