O2 levels are generally at the lowest just before the lights come on, not in the middle of the night. That is, unless the tank is hit by enough room sunlight to stimulate photosynthesis from natural dawn.
Hot weather can be problematic and may require aeration from a mid-point in the dark phase until lights come on as O2 levels will be lower. Low O2 is much more likely to be a problem for the fish than high CO2 when using yeast and sugar systems.
I have not used this kit, it looks impressive. I have used yeast and sugar 24 hour CO2 for years on tanks with zero problems to fish health. I have also used high pressure cylinder CO2 24 hours with zero problems - using roughly a 1/3d of the bubble count for solenoid controlled injection. I found 24 hour CO2 injection produced good plant growth with stable conditions and less algae with lower CO2 levels in the water than is normal with timer controlled CO2. Increasingly regulators come with solenoids, this encourages on off use of CO2. My experience is not the same as every one else, but I have only experienced loss of fish with CO2 injection in unusually hot weather, the larger heavier fish require a lot more O2, I have learnt my lesson, and in the hottest weather even with a solenoid on my CO2 system, intend to run an air stone to increase O2 during the dark phase, which will of course, probably unnecessarily, gas off much of the CO2. Funnily enough I did this thirty years ago when I was nervous when first using CO2 injection. For about 26 years I had no problems but the heat wave of 2022 caught me out and I lost Rosy barbs - fish of course which actually are happier in temperate water rather than tropical.
Let us know how you get on with the kit, using yeast and sugar is easy and less bother than citric acid and bicarbonate and more environmentally friendly than high pressure cylinder CO2.
Two weeks is the minimum timescale to see much improvement in plant health, but with good lights and CO2 you should see some O2 moving in the leaves towards the surface of the water, in at least some plants, towards the end of the photo period. Success does not require the fizzy drink pearling that can be achieved.
