Usually I just make my own jerk marinade, but if I were to use a commercial marinade, I would salt my meat then add the marinade. One hour is honestly plenty, but if you want to go longer, a half a day is good. If you want to marinate a whole day, sure. I'm just telling you that it's false that there's a real difference in flavor and that depending on the marinade, it's detrimental to marinate that long.
As for the other ingredients, I honestly believe people use a lot of superfluous ingredients when marinating because there is a mentality of more is better instead of considering what each ingredient adds. If I were using a commercial jerk marinade, I'd test it to see if it was spicy enough for me. If not, I'd sprinkle meat with some form of dried chile pepper or use fresh as your boyfriend did because the oils in the pepper definitely penetrate the meat. If I thought it needed acid or sugar, I'd add a bit of those.
But marinating with cilantro doesn't give you much flavor. If I want cilantro flavor, I make a wet rub. Just mash it to a paste and rub on the meat. I'd add some onion in that paste, too, if I wanted a bit of onion flavor (though they do work in marinades). Being in a marinade won't really do much unless your marinade is basically cilantro pesto. Cilantro and other delicate herbs just don't pack as much punch as herbs like thyme and rosemary in marinades.
The only thing you have to worry about with breasts is over-cooking them because unlike thighs, they are easy to overcook. That and they have less flavor. It doesn't make a difference in terms of how the marinade works.