I had problems with an Aquatica vacuum system as well. At least half the time, I couldn't get it to turn on by pressing the button before closing the housing. I had to take the battery out and replace it each time to get it to function at all. Behavior was erratic when pumping out the system. Sometimes it would work as expected, turning green after about 15-20 pumps. Other times I would pump for a long time (counting over 75 pumps) and it was still blinking yellow. Only about one dive in four was it still indicating a vacuum at the end of the dive, though the housing appeared to be functioning fine.
As I was out on a liveaboard at the time there was nothing I could do about this, so I ended up largely ignoring the vacuum system. That trip ended with my first ever complete camera flood, after 700 dives with housed SLR cameras. The cause of the flood isn't clear, but Aquatica & Backscatter are replacing the vacuum system as part of refurbishing the housing.
I will be bench testing this system very carefully when it comes back. The design of the main seal on the latest generation of Aquatica housings makes it nearly impossible to do a visual inspection or run my finger around the o-ring. So that vacuum system isn't just insurance, it is a critical part of closing the housing.
I would call the second damsel Dascyllus trimaculatus. In Fiji they usually have orange bellies. Note that most of the ventral & anal fins are dark here, rather than all orange as they should be on D. auripinnis. You can also see a hint of a white spot on the body.