SFML is a native C++ library (not just C with classes). If you include any of its headers, you will end up pulling in a lot of C++ headers as well. I'm not certain, but in older Visual Studio library versions, a lot of the C variadic function stuff was implemented using monstrous macros. Those macros might be clashing with the proper C++ implementation now that you've included something that is C++. You should probably try to clean out the old C function stuff (strncpy, sprintf_s, etc.) and replace them with true C++ code.
warning C4002: too many actual parameters for macro 'sprintf_s'
This especially, has me wondering how the code even compiles in this case.
Basically, you have the warnings turned on already, before transitioning to SFML, make sure to fix all those warnings. From what I can tell all of them are the result of archaic C code being used. There are far better C++ alternatives, and I'm sure a side effect of replacing the C with C++ code is that SFML will eventually just work as it should.