Every Protools version has a limit to how many active 'voices' you can have.
I say voices because auxiliary tracks and instrument tracks don't count; It's just tracks that contain audio.
PT allowing you 16 seems very low, but I'm not up to speed on V6.4 specs, so maybe that's right.
Dyn means a voice is on, off means off.
You can consolidate to an extent because a stereo track counts as one, but two mono tracks count as two, so if you recorded something onto two mono tracks, consolidate them down to stereo. That'll save you some tracks.
Other than that, the only way to cut down is to bounce groups of tracks down to Stereo.
Maybe you could bounce the drums down to stereo and save yourself a number of tracks.
You can always keep the originals (temporarily disable the tracks) so that you can go back in the event of a problem.
Basically, you're going to have to delete stuff, change your daw, or learn to juggle.
Personally, I'd google reaper to find out if it has a limit. If not, I'd jump ship, for this session at least.