Hey, changing the sample rate to a higher one does reduce the latency, but of course the patch must be able to run stable enough at a higher rate for this to work.
You may edit the whole command line for the Jack server in /etc/jackdrc file. Check out the ‘-S’ flag here: Latency Measurment with jack_iodelay, it may be able to reduce the latency a bit, but might turn out to be a less stable in case overruns occur, so experiment with it.