Dwarf lionfish tankmates

[teamA]

Hello, I have a reef tank with 2 dwarf lionfish (dendrochirus brachypterus). I have them for about 3 weeks (tank is functioning and stable for about 2 years but I lost all fish in brooklynella outbreak 6 months ago; the tank has been fishless until adding the lions now) I'm not sure if they are a pair but they always interact peacefully, there are no signs of aggression.
They are currently both about 6-7cm long. My tank has a 64 gal display and 79 gal overall volume. I have oversized skimmer (Arka ACS 180).
My question is:
- can they be kept together long term? Or is it too small a tank for 2 adult dwarf lionfish?
- can I add any other fish? I was thinking about adding dwarf angel, e.g. Centropyge bicolor

 

[Baby Damsel 219]

damselfish would be good like 3 stripped and dominios another could be big angles