My friend,
I'm a VC++ developer with extensive experience, but not necessarily in games.
DirectX APIs have changed a lot, to cater for new graphics cards, and other new technologies related to gaming. So , your best bet is to upgrade the entire source code to VS 2015 or higher, and DirectX to DX 11+. This may help,and then we can look in to changing any function calls that affect FPS matters.
Let me know if you may be interested, and I will take a look at the code and build it on My development machine,