Do you use NFS mounts that would hold Pi-hole's database files?
Did the file jump to grow to that size only recently, or has it always been about that size?
Your debug log shows that you've enabled Pi-hole's Conditional Forwarding, which may result in a partial DNS loop, depending on your CF target's configuration.
Did you switch or change that only recently?
A partial DNS loop may trigger ocassional short spikes in CPU load on certain requests and excessive logging of repeated requests for identical domains, which could have contributed to a growing log size, and also to the long term load warnings in your debug log. Redacted parts of your debug log may have allowed us a glimpse at actual queries, which could have revealed such a loop.
However, those loops are also guarantueed to trigger a specific dnsmasq warning, which is completely absent from your debug log, while there are almost 30 long term load warnings.
This would indeed suggest another cause for the load (and your debug log shows that there a quite a few other processes running besides Pi-hole).
Would you be able to attribute those load peaks to some other process's activity from the times of those respective log messages?
Those warnings can be reduced to two variants:
*** [ DIAGNOSING ]: Pi-hole FTL Query Database
(...)
TEXT value in query_storage.domain
TEXT value in query_storage.additional_info
Let's have a look - what's the output of:
pihole-FTL sqlite3 /etc/pihole/pihole-FTL.db "SELECT domain, max(timestamp), count(*) FROM query_storage WHERE typeof(domain) = 'text' GROUP BY 1 LIMIT 10;"
pihole-FTL sqlite3 /etc/pihole/pihole-FTL.db "SELECT additional_info, max(timestamp), count(*) FROM query_storage WHERE typeof(additional_info) = 'text' GROUP BY 1 LIMIT 10;"
But together with long term CPU load warnings and the database lock messages, that also makes me wonder whether you would run some third-party scripts that interact with Pi-hole's query database?