Hey, similar situation here!, well, kinda...
I'm 17 and moved out of my mum's place just over a year ago, and it has been the BEST thing I have EVER done, but the only way it was possible was through tricking my Mum into beleiving that I was only going to be staying at a family members place for 2 weeks... there was so many threats and manipulation on her part previously, she was unwell, as in she never has looked after herself properly with diabetes and life in general.. she knew there was something wrong with the way myself and 13 year old sister and 23 year old autistic brother were 'looked after'. "Don't say that at school", "oh, make sure no one sees that or..." continuously occured durring my childhood and early teens... lets just put it this way, trust me, it was dreadful living there for so many reasons... Iwasn't really able to sustain any type offriendships bcozof it, and my Mum also is paranoid about control and 'safety', not even could I go down the next ile while shopping without my Mum being able to see me... in case I get raped, murderedand etc... and with my Mum she didn't want me to start driving till I'm 25!!!
, as she said that apparently your brain doesn't stop developing untill then -_-
I now live with my cousin, his gf, and two other ppl in a shared house, which has been pretty good the last 6 months
anyway, enough about me... :P ...I think you obviously want to live with your boyfriend, and have good reasons why to leave, but just concerned how to break it to your parents and what shall happen after that, so your wanting to wait untill your 18, which I can understand. If living there really is as bad as you describe, I say just go, why should you continue to suffer durring those 2 months? and also knowing at the same time that you have this ideal life in mind with your bf, making it harder on yourself. The fact that your parents are your guardians untill your 18 doesn't really mean much, trust me. Whats so good about being 18? what do you think will really change between now and then if you choose to stay with your parents durring the 2 months? About your parents, who really cares what they think initially, they've treated you so badly and have had so much time to try and change there ways to help benifit you. You can be so much better of, by the sounds of it, if you just leave, your gonna leave when your 18 anyway right? thats only 2 months!
Anyway, goodluck! hope it all works out!