I have talked to my Mom and Dad humbly and in a nice manner, telling them they're not heading down such a great path. I have tried to say it in different ways -- straight forward and not so straight forward. I some times feel that perhaps I should just let it go and let them get taken advantage of. They haven't listened to me in the past, I'm not sure they listen about this. If I find anything I will tell them. All I am saying is they probably won't be receptive and that I wouldn't be sad over the fact if they lost a lot of stuff. From my own experience, it is when you have nothing and you find yourself on your knees with nowhere to go it's easier to see where God wants you to be and that you should submit to Him.
One of the reasons I suggested you should gather facts and present them to your parents with little or no commentary is because of the very reason you mentioned. It is one thing to hear a personal opinion that can be easily dismissed, it is something else to see a hard fact that must be considered and dealt with. Growing up is a struggle for you, but it is also a struggle for your parents. They still see you as their little boy. Outside evidence changes it from their little boy to others.
You are right that hardships are an excellent teacher, but it is not proper to wish ill on anyone. "Do not rejoice when your enemy falls, and do not let your heart be glad when he stumbles; lest the LORD see it, and it displease Him, and He turn away His wrath from him" (Proverbs 24:17-18). If this is true for an enemy, then it must also apply to a loved one. "He who mocks the poor reproaches his Maker; he who is glad at calamity will not go unpunished" (Proverbs 17:5). It is good to desire that someone learns. It is bad to desire that they learn through suffering.