Hello Eva,
Sounds like you are where most of us were when we learned about BP - I know that as scary as it sounded, there was comfort in knowing there was a path through the chaos of life I had been living. As far as I know, you are 100% right in saying that there is no known cure for BP - just treatment. Having said that - once you find the right treatment, although it may take a while to narrow down the right mix, most people can lead average, healthy, happy, productive lives despite the BP diagnosis provided they are diligent about their treatment. Since the very nature of BP is cyclical, managing the extremes allows many people, myself included (I'm 25 too), to minimize the amount of medication that we take as a whole.
I don't know the stats on the whole inherited portion of BP, but I don't think that just because you have it, your son is garanteed to have it. I think it does increase his risk of developing it later in life, but the fact that you have experience with the disease will give your son a better chance of understanding and being able to deal with that possibility.
I hope that you find some information and support and welcome to HW,
Putter