OK, with token in hand we see the problem.
pihole-FTL is not running (but is trying to run). The reason it isn't running is that in the previous 24 hours, you had the following activity on the Pi-Hole (from the tail of the pihole-FTL.log near the end of your debug log). The offender here is the 3,263,220 queries in that time (that's a lot). These queries are likely circular traffic between the Pi-Hole and the router, but could be another problem.
[2019-01-01 23:26:25.138] -> Total DNS queries: 3263220
[2019-01-01 23:26:25.138] -> Cached DNS queries: 7639
[2019-01-01 23:26:25.138] -> Forwarded DNS queries: 3254018
[2019-01-01 23:26:25.139] -> Exactly blocked DNS queries: 1544
[2019-01-01 23:26:25.139] -> Unknown DNS queries: 19
[2019-01-01 23:26:25.139] -> Unique domains: 859
[2019-01-01 23:26:25.139] -> Unique clients: 7
[2019-01-01 23:26:25.139] -> Known forward destinations: 7
When pihole-FTL starts, the default behavior is to read the previous 24 hours of data from the long term database. The same section of the debug log shows FTL allocating more and more resources until your Pi runs out of RAM and mis-behaves.
[2019-01-01 23:26:23.151] Notice: Increasing queries struct size from 3220000 to 3230000
[2019-01-01 23:26:23.550] Notice: Increasing queries struct size from 3230000 to 3240000
[2019-01-01 23:26:23.979] Notice: Increasing queries struct size from 3240000 to 3250000
[2019-01-01 23:26:24.469] Notice: Increasing queries struct size from 3250000 to 3260000
[2019-01-01 23:26:24.970] Notice: Increasing queries struct size from 3260000 to 3270000
The solution is two fold - first we move the long term database to another file name (so you don't lose all the data, or you can just delete it if you don't care about the previous data), then restart FTL with conditional forwarding off (your current setting) and see if behavior improves. We use the methods described in this part of the documentation (Redirecting...).
sudo service pihole-FTL stop
sudo mv /etc/pihole/pihole-FTL.db /etc/pihole/pihole-FTL.db.old
sudo service pihole-FTL start
This should get you up and running again. Watch the number of queries for the first 24 hours. If they start climbing rapidly to the millions, the root cause is not corrected and the problem will recur. If they stay in the tens of thousands (typical for a home network), then you are set.
And, don't forget to put your router back pointing to Pi-Hole DNS only, and remove the entries that bypass Pi-Hole.
This thread from a few weeks ago is related: