the Nvidia ##40 series are their lowest end video cards and it's already quite a bit old. FYI the "tens" tell the performance level compared to others sharing the same "hundreds". Agreed, it's much better than the minimum requirement but it's still not much. You can't expect it to run AH3 with all the bells and whistles enabled.
That said, you should be able to get better than 13 fps. Start by disabling all enhancements and set all video sliders to their minimum. Anti-alias and environment mapping are the biggest resource hogs. Mark the performance, then enable one feature and see if the performance drops. Disable that, enable another. When you find those that don't hurt too much, try two at a time. It's tedious but there's no shortcuts. Then again, none of the features are required in a fight!
I've been using
https://www.videocardbenchmark.net/high_end_gpus.html as a reference, comparing the G3D rating of my card (whose performance in AH I know for sure) to others. Back in the day when AH3 was new I came to the conclusion that cards above 3000 marks should give 60 fps in most situations on a 1920x1080 screen. See how your card compares with the minimum and the recommended minimum cards:
