If I want to own just one BTC, suggest the best strategy to do it.
How many do I need to buy monthly?
How long before I achieve the one BTC target?
How do I stop myself from selling before the 1 BTC mark?
As far as I can see, you have a problem already at the start, because obviously at this moment you cannot control yourself, which would mean that even trying to achieve your goal will be unsuccessful. Therefore, I suggest that you first learn how to control yourself, and when it comes to self-control, you have countless tips online.
As for how to buy and how much, as far as I can see you are writing, and maybe you have some other skills that you can offer in exchange for BTC - if you also have a regular job, just set aside a certain amount from all this on a weekly or monthly basis and buy BTC. However, I would advise you not to set such a high goal to begin with - start with reaching 0.01 BTC, and then gradually increase it. That way, you have a much higher chance of reaching your goal one day.