Hey man, I'm very sorry for your troubles. I've been playing this game since the beginning of S2 and am currently Diamond. I can tell you right now I am fed up with the amount of toxcicity in this game, however the greatest asset rito has given us is the mute button. Abuse that thing. If people threaten to leave, don't respond. For someone who is so close to getting out of bronze, here is my biggest tip. Choose one or two champs than can play most roles, like ezreal or zed and master them. Play a TON of normals and shift to ranked. You will significantly improve your in game play. Next I suggest finding someone of equal or slightly greater skill level as yourself and play with them alot. Get used to their play style and play alot of ranked. The only way to rank up is by playing the games. People leaving is difficult to manage, however, when you rank up out of bronze, they will be waiting for you in silver, gold, plat, etc. That's all I can offer over text, however if you want to talk more add me in game and I can help you out. :) Good Luck.