Every one of your questions are the ones that are dangerous to answer.
I can tell you a few things.
My 32 S&W bullets are all either 68 grain lead or 71 grain FMJ so any bullet in that weight range should suit you well.
Small pistol primers are the only option. The brand is up to you, however you should pay attention to a good reloading manual for the correct primer/powder blend.
You really need to refer to a loading manual like the Lyman, Speer, or Hornady. All of them are focused on their own bullets. However, you should within reason be able to work up a light load with most lead bullets in the weights and shapes they recommend. Read them to find the correct powder for the velocity your looking for. Cowboy loads are generally on the lighter end of the loading spectrum so you have much less recoil but can still send the bullet downrange.
I don't cowboy shoot but have friends that do and they have their own recipe and most of them shoot 45's, so they won't be much help either.
I know I'm probably not telling you something you already may know, but the question is an open one with way too many variabbles to give you a sold answer.
You might get lucky and have somebody here that shoots cowboy competition and can give you a working recipe.
Regards,
Gearchecker