Dear Andre,
I have experience with several WiFi 802.11 setups but not with netjack, which IMHO is the least suitable solution. If u want still to go on that way I suggest to increase the period size, to allow the network to hand buffers in and out with shorter deadlines, I guess that should help.The other way is using jack clients such as jacktrip or nj-bridge. I employed those for networked performances over the internet or wireless and tolerate some jitter, just adjust the buffer size at the expense of latency (not a big deal in your use case). Nj-bridge may be more suitable to you as it instantiate mono directional flows.
Best
Leonardo
http://a3lab.dii.univpm.it/research/wemust