Of course its not going to stop it but its supposed to bring awareness to the problem so that people that feel the need to commit suicide know that there not alone and that there are better options instead of killing themselves.
If you really like him and you really want to be with him then you should go somewhere and talk to him and tell him how you feel and make sure he knows that he cant be flirting with girls. Just work out all of the issues you have before you start dating again
If I were you I would text him from a number he doesnt know and pretend to be a guy and say youve been with his gf for the past couple months and that he needs to go... thats just my opinion but you should also think that if he is your bestfriend you would want him to be happy and if he loves her you should be happy for him