Yeah, my apologies, I keep getting the 'load' and CPU usage mixed up on this Linux thing.
The load is high, the CPU is not, as according to 'htop'.
I do not currently have IPv6 connectivity, and didn't pick it during install (though I did have it enabled pre-4.0). The website linked also states 'No IPv6 address detected'.
Copypasting in the echo above seems to do nothing, but as said, Linux novice, I might possibly be doing this wrong.
I did find a site talking about the NXDOMAIN thing while trying to troubleshoot before posting here, I didn't quite manage to get it done though, will try again and get back to you.
Thanks for the help thus far,
Edit:
If I'm doing the NXDOMAIN thing correct ('sudo nano /etc/pihole/pihole-FTL.conf'?), then there's nothing in this file. Should I just add 'BLOCKINGMODE=NXDOMAIN' to it, save, reboot the device?