FTL issues: Connection refused. Is FTL running?

About those loggings, if you setup your network like described in below link, you wont see those NTP time sync queries coming from (probably?) your router no more:

And about size of the pihole.log file, yes its exceptionally big compared to mine which is only 2.5MB.
But that is to be expected if your router queries Pi-hole that many times a second probably to sync its clock via the NTP protocol.
I dont know what limitations are concerning log size and pihole-FTL.