You could use the Glide3x Wrapper, but it's far from perfect at the moment.
You could also use Fraps, available from www.fraps.com for FPS measurement in Fullscreen. Though to be honest I am pretty dubious about the accuracy of this with Jabos plugin.
Try using Jabos D3D 1.4, if you haven't already. I say this simply because, that is the version I tested.
Certain games (or in this case plugins) don't write a certain value which FRAPS uses to judge the framerate, so in that case you won't get any reading whatsoever. The writeup about this problem is on the Fraps webpage.
I said this earlier, and would actually like to take that back. It does seem to be very accurate (with the FPS limiter on, it runs at a constant 30FPS, without it climbs a lot higer).
Unsure, that happens to me as well. However, it doesn't seem to be a problem with the emulator, as fullscreen shows 30FPS constant - unless I turn off the Frame Limiter, in which case it goes much faster. I like it the way it is though, very smooth and nice.