And two days ago, my public IP changed automatically (expired DHCP lease time from ISP) but the behavior is the same. It never gives me the correct cached IP for DNSExit under cached IP but the actual FQDN (as accessed from the outside) updates automatically. So it seems to me that the only problem here is the display in pfsense. It is not correctly updating the cached IP.Well ... the idea is that when your WAN IP DID change, the update against DNSexit should work, with some sort of "Success" result. The "Success" result will have as effect : a new cache file is created with the correct IP.
You need just one reverse proxy (and really only one can listen on a particular IP/port combination). Are you already using Squid as reverse proxy?