check please the contents of the following file:
/var/lib/openhab2/config/org/openhab/mqtt.config
if they correspond to the settings that you have in /etc/openhab2/services/mqtt.cfg
If not, shutdown OH2, delete the mqtt.config (not the mqtt.cfg) and then restart OH2
Now, for the other issue:
can you post the contents of your /etc/mosquitto/mosquitto.conf