Block failed connection attempt to wifi

Can I block clients connecting to the router after some failed attempts (password wrong)?

Yes, there's software and firewall rules that may accomplish what you desire. I'm not sure if any of the software is readily available on OpenWrt.

Are you asking about the HTTP GUI or SSH access (I ask because I have an SSH firewall rule you may be interested in)?

Is yours the one linked in the old forum?
Both would be useful to have.
Finally is this enough to prevent any access from outside the network to ssh?

iptables -I INPUT -p tcp --dport 22 -s -j ACCEPT
iptables -I INPUT -p tcp --dport 22 ! -s -j DROP