If you are worried that the skimmer is damaging the octopus, turn it off for a while and see if the octopus stays there or not.
As for your light cycle, I wouldn't be planning a dramatic change. Over time you should be able to ween the octopus to a longer cycle, just don't do it quickly. Maybe a half hour more per week, as long as the octo seems used to the cycle he is on already. If the red light is the only light reaching the tank during the day, I suggest increasing that to give some daylight to your pet. Red is difficult for an octopus to see, which is why it is used for moonlights and is great for nocturnal species. If the octopus you have is truly Abdopus Aculeatus
, it should be diurnal and I would guess that it hiding is just because it is not used to it's environment yet. With just red light and no light, you aren't giving your octopus much of a variation between day and night and it is probably going to stick to the schedule it had in the wild longer than if there was substantial difference. Remember if you do plan on changing the light cycle, do it slowly so you don't shock your animal.
Also 80 to 94 seems extremely hot for any species, though I am not a researcher
Glad to hear Kenny is getting more interactive. I hope your good luck with him continues.