Given the numbers that you have presented, you cannot afford to go to BU. There is no way that you could borrow enough, and to even try is likely to be a disaster.
Sadly you need to find another option. If you don’t have another much more affordable option, then you are going to need to either go to community college or take a gap year.
Most students are constrained by financial issues in terms of what schools they can attend.
By the way, thank you for telling us about this situation. I think that this is helpful to other students to get a sense regarding what they might or might not run into when they need to apply to universities.