When you read this, imagine a loving aunt saying this with popcorn on the couch, not a mean jerk. This will read like criticism, and I guess it is, but it's really designed to be constructive criticism instead of insulting.
I don't think you should graduate two years early in order to go to a science field when you've only got Algebra 2. Your youth is a handicap to schools, not an advantage; they want to see that you have maturity AND academic preparation. IMO, you show lack of maturity by being in such a hurry to move on without having taken the opportunities normally available to someone your age, and lack of academic preparation by only having Alg 2 when you want to go into science.
As far as your question goes... I don't have experience with the packaged curricula. But as a homeschooler, can't you make anything more rigorous by reading all the books instead of a selection, or using 5 sources instead of three in your papers, etc.? Another option is to delay graduation a year and take some community college classes dual-enrollment with your homeschool so you will be more attractive to four-year schools. It's important that you do dual-enrollment so that you aren't forced to apply as a transfer, which is harder in many schools.