Basically some subjects will most likely get cut from B Eng and B Comp Sci. Since you are doing honours it is most likely, B Eng will have more credit points that need to be complete.
Generally work experience is not that important in high school. I would think emailing or contacting people through business websites could be better idea in case people are busy.
I think polynomials was part old syllabus. But the theorem you are looking for is rational root theorem. This should provide the answer a/b.
https://en.wikipedia.org/wiki/Rational_root_theorem
I don't know what to say. I think it is up you make decision. Maybe looking into resources you are for studying if you decide try macroeconomics again. For math subjects I prefer to use textbooks with fully worked solutions and that are available online or on Quizlet. It might be worth looking...
a_y = -g
a_x = 0
v_x = C_x
=> v_x = u
v_y = -gt + C_y
=> v_y = -gt
So you need to resolve the components. What does x/y components for velocity and acceleration equal to. After that it is basic trigonometry.