You wouldn’t be expected to take a class above AP Spanish Lang. Once in college, you may want to take more classes (such as Spanish for Professions, which may require an extra preparatory class. If you arrive with Calc3 completed there shoukd be no issue with fitting it onto your schedule.)
Your GC’advice is 100% correct. If your SAI is negative, your best bet is one of the highly selective/generous meet need colleges that offer Engineering. These would include Penn, Dartmouth, Cornell, or Vanderbilt, Duke, Northwestern. These would cover all tuition, fees, room and board (housing&food), but also books and transportation. Other universities that aren’t as high a reach would be Lafayette or Lehigh.
Finally, you’ll need to investigate programs for lower income students in VA, to insure you can afford VTech.
In addition, as someone said upthread, keep Questbridge in mind. They have Junior Scholars for the summer. The Questbridge application is due early in the Fall of senior year.