I have been  struggling for about a year with the flaky DHCP server on a standalone router I decided to switch to pi-hole for DHCP and DNS service. 

1. DHCP loses its DHCP lease database upon restart. I am not sure what is being done to preserve the database during reboot but the bigger problem is starting the DHCP server before time has been synced. The device apparently does not have its own RTC.

Please do not start the DHCP server before the time is synced. The extra few seconds to wait for the time to sync during reboot is nothing compared to messing the DHCP lease database.

2. I am at loss what I am supposed to query via SNMP to get bandwidth info. I queried  IF-MIB::ifHCInOctets for all interfaces and its 32 bit counterparts and found nothing reflecting the actual bandwidth. Can the SNMP agent on the router be updated more frequently? The current interval is 15 seconds. Can it be lowered to 1s?