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 192.168.1.1 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.