As someone who managed to make a clean break from the religion at the age of 20, it sounds to me like you're already making a good start. Not hanging out with Witness kids and trying to avoid 'spiritual things' is going to be a huge help. If you're really 100% done with the religion, do not give into the pressure to get baptized. If you don't get baptized, then you can honestly say that you never chose to be a Jehovah's Witness.
What helped for me was getting a job. For whatever reason, my parents eased up on me a LOT once I started working. My job allowed me to skip every Sunday meeting, avoid Saturday morning field service, and because I would get home from work about an hour before the bookstudy, I'd just say I was too tired to go to that too. So I ended up going to maybe one or two meetings a week, at most.
Making friends outside the Kingdom Hall is great. It helps you get used to normal socializing, not to mention the fact that they're not going to bug you about your field service hours or ask when you're going to get baptized. Not to mention, they're way more fun to hang out with and you don't have to hide who you really are around them.
As for the baptism, luckily I wasn't under too much pressure, but whenever I was asked, I just told them that I wasn't ready yet.
Tell your Mom that you're not really comfortable doing a study with this guy in your hall and that you'd rather study alone. Then do the shittiest job of studying that you possibly can (my method was to speed read and just highlight whatever looked right). It might be enough to satisfy your Mom.
Definitely save up money for moving out, and if you do have 'worldly' friends, see if maybe you can arrange a roommate situation with them so that you can move out once you turn 18. Or better yet, try to move a bit farther away, so that your absence from the Kingdom Hall won't be noticed.
But once you move out, that's it, you're done. You don't have to live this lie anymore. I've been to one meeting since I moved out of my parents - a Memorial, and it's been getting close to 10 years since I've moved. You're in a position where you should be able to make a really easy, clean break from the religion without any of the heartache that people who have been trapped for years have had to go through.
You can do this!
in concert twice, and very loudly and happily sang "Hail Satan!" along with them.