Here is the algorithm.add method for dual mining with decred:

Please take a look at our documentation:
https://github.com/nicehash/excavator/tree/master/api#-algorithmadd (example 2)

Here are the ports for different algorithms:
https://www.nicehash.com/algorithm

Remark on your config file:
You added OC settings on "on_quit" event, this will take affect when you quit application. In order to change OC settings before, you should change the  {"event":"on_quit","commands": to {"time":5,"commands": for example. 

For temp settings take a look at device.set.tdp (thermal design power):
https://github.com/nicehash/excavator/tree/master/api#-devicesettdp

Note: You could always set your OC settings with a third party software (MSI Afterburner) and just run excavator without device.set* methods.