Just a suggestion for your forth choice.
If you can handle a 4th, i'd suggest History. Its a classical subject and I mean, it's mainly content which will make a change from the technical side of grammar that you'll get from the languages.
I got a C in GCSE History because i fell asleep in both exams...long story lol and despite arguing with my school that I could pass this year, I got an A in my first unit in January.
Classic.
& on the note of studying a lanugage by yourself, if you're commited its the best. I speak portuguese but I had to teach it to myself because I never knew anything about the grammatical side. I had my portuguese AS exam today and still haven't experienced a set back in not having a teacher.
Every persons different, but its worth a try, languages are AMMAZINNN.