Do the PPL, by all means if you can pull the money together do it in parallel with your Highers. I think that finishing your Highers is a very good idea, as you'll ultimately want those study skills.
"Applying" to an FTO is no big deal - they want your money, you just need to prove not a complete liability. But for your own protection and knowledge, you want a PPL to tell you if you have the aptitude and enthusiasm for flying to take it any further. Do tell your instructors that you are considering going "pro" and want treating as such.
I agree about degrees not being for everybody, but have something as a backup skill - for example sports coaching, lifeguarding, basic food hygiene that will allow you to make a living whilst you aren't yet being paid to fly - odds are you'll need it at some point.
G