Also this, having a " plan B " is a good thing, so it is a good idea to first do some college degree, so you have something to fall back on.
I also want to mention that before you take any flight lesson ppl training do your class 1 medical instead of a class 2, i don't have to explain the dissapointment when you are half way and not medical ok for the cpl !
to answer directly on your questions:
1. Do what you love and want to do for a job if you could'nt become a pilot
2. Depends on type of course and what FTO, general this will be starting around 50 k € up to +100 k €
3. For the ATPL you need to know fysics and some math, so it's a good thing to brush this up , but this is not rocket science, the theory is more or less like college level, BUT it is a lot in a very short period !