What do these numbers mean?

I am playing Falcon 4 BMS and did some tests with my GPU and my screen configuration. I have four 1920x1080 screens and I Eyefinity three of them for my main game display and use the fourth one (touchscreen) to control various switches in my pit. My Eyefinity resolution is 5896x1080.

In my test mission, I would get anywhere from 13-16fps in the slow areas and 17-22fps in the better areas. I noted some numbers via MSI Afterburner and noticed that my Core goes to 1050 all the time, the Mem goes to 1500, and the Mem usage ranges from 2200-3000. However, GPU usage says anywhere from 43-67.

Is my GPU struggling with this game? Or does it have muscle to spare?

Considering that you're talking about a 1998 game, it's most likely single threaded.
That being the case, it's most likely that your CPU can't keep up.

OC the CPU and see what happens to your FPS.

Well, the numbers for CPU usage range from 57-77 or 75-94 depending on if I'm playing it windowed or fullscreen. Surprisingly, windowed mode is the one with less usage. CPUID reports around 60-89 usage on windowed mode and 75-91 on fullscreen mode.

I can OC the CPU but I was asking about the GPU.... are you saying my GPU isn't working hard at all?

I'm saying the CPU has the GPU held back, that's why the GPU isn't fully loaded.