Fenner gave great fish advices.
68 is still young I think. 85-90 is the going marker now.
I don't think you actually check out in your sleep.
You probably get a big jolt with a lot of pain on the way out.
I am a fan of ozone. I use both UV and ozone together, too. Ozone is great for water clarity. I have both redsea and Poseidon but redsea is my go to unit due to efficiency. I flush it out with water to recharge the unit on a yearly basis.