Preparation of the CO2 system

Hi,
I am looking for a good solution to use CO2 for my grow room, currently, I have got one solution to use CO2 metal tanks, which seems to be a good and acceptable solution for me. However, before I start using it, I would like to know some details and if all my calcualations are correct.

So my room is 5,3x3,3x3,3 meters, which makes it 57,7 cubic meters. (2040 cubic feets)

My room is well sealed and has a good air circulation (if needed). So what I am planning to do, is put the CO2 tank and use it this way with the 18 hours of ligh.

2 hours of CO2 leak + ventilation OFF
30 minutes of ventilation + CO2 OFF
2 hours of CO2 leak + ventilation OFF
30 minutes of ventilation + CO2 OFF

So it would be 14 hours of CO2 leak during the day.

The question is, would this type of CO2 usage be good enough or should I do it something like this

8 hours of CO2 + ventilation OFF
1 hour of ventilation + CO2 OFF
9 hours of CO2 + ventilation OFF

I am not sure on how to do this better, because the heat of 4000 wats (HPS) is quite huge and I can not work with CO2 without ventilation at all.

Any solution would be much apreaciated!

P.S. How sealed the room should be? Can it have some sort of small vent holes when the ventilation if OFF ?

if you can exhaust your whole room in less time, 30 mins is not needed.
i dont vent my room whatsoever. but i am thinking of venting on a similar schedule as you