I had the d3dx9_39.dll and (0xc000007b) issues, and it's taken me a good three hours of steadily growing insanity and bullheadedness, but I think I've managed to finally grasp and (so far, at least) solve them!
The answers in this thread and on google were almost no help. Downloading the dll in question and putting it in either the game folder or my SysWOW64 folder got rid of the d3dx9_39.dll error, but it was then replaced by the (0xc000007b) error. Installing the latest .NET frameworks did nothing, changing DPI settings in the compatibility section of the exe's Properties did nothing, installing and attempting to use Locale Emulator did nothing, and a number of other suggestions (mostly from googling, but a few here as well) of what to try seemed too off the mark for me to attempt them given how high-effort or even potentially damaging they sounded.
So, the problem – as I understand it from further research, anyway – is that FOBS is looking, very specifically, for a d3dx9_39 dll, which belongs to a specific version of DX9. I have DX12, but going into my SysWOW64 folder, it's apparent that my installation also came with DX9, 10, and 11. But my relevant dll there for the DX9 installation is 'D3DX9_43.dll', from some later version of DX9 than what FOBS was expecting to find. I assume that just pasting in the _39 dll I downloaded fixed FOBS's "find the expected file" problem, but that the _39 dll was somehow incompatible with my actual, more up-to-date _43 installation.
Thus, my solution: go to your SysWOW64 folder, find your particular d3dx9_## dll, place a copy of it into your FOBS game folder, and then rename that copy to the expected 'd3dx9_39.dll'.
Doing this has at least gotten me to the title screen, so it's more progress than anything else has managed to give me. Hope this helps anyone still struggling with either of those issues.