Please accept my apologies for my late reply. I did some research and found out that almost all schools seem to have problems with Filipinos and Africans, who can't speak, neither teach English.
Here's my five baht to your situation:
Try to stay in this program and "report" this Filipinos wrong speech. Very good would be if you record him with your mobile phone, when he says something wrong. Try to get more students from your class on your side, as one person alone is never really strong.
But what would be, if ten, or more students complain about his poor English? That would be his end. I guess you remember "Brian" from Ubonwitt and his wife, plus all the other Filipinos. They shouldn't teach English, as they can't even have a decent conversation with somebody who really speaks in English.
You're in a very difficult process now. First, you're getting older, there're so many things that you've never thought of that come to mind, right?
Another point is positive thinking. Once you understand that to get your body and your spirit in harmony, there's nothing that can bother you anymore.
Don't take your ability in math so serious, I always hated math and it was because I hated my teacher. I was such a "bad guy" that he left school and started to teach in Africa. I had to leave school as well and went to a private school afterwards.
The whole problem is also called life. There'll always be things that make you crazy, but it's just the way you look at it. There's an old saying: "life's a bitch. " But life's also a present and trying to find the right way isn't always as easy as some people might think.
You've already reached a pretty good level of English for your age, many Thai English teachers couldn't even write such an e-mail you'd sent to me.
Now just calm down, do some meditation, do some online stuff to get better in math. You'll be surprised how many free programs there are. Then try all to get this Filipino out, if he can't change.
Tell your mom that you've found the solution and all will be fine. Please think about all the money they're paying for your education.
Stay in this program, you've got air conditioners and many things would be completely different in the outside program.
And finally, never forget that you can contact me whenever you encounter a problem. You're just having a rough time, don't let that bring you down.
I hope I could help you with my pint of view. Please enjoy your life and focus on your future. Wish you the best from the bottom of my heart. Just don't give up so easily. I see life as a way full with stones. When I go my way and there's a stone, I take the stone away and I'm still on my right path.
I wish you a good week. Just smile when you read that and go for it. You're too clever to give up.