I'm saltier than the Dead Sea

I've been playing League from 2012 Christmas, it was season 2 in ranked. My friend suggested to try LoL and - ofc - I got hooked from the very start. Back then (my friend was really toxic back then) I couldn't even understand how anyone could get so upset about a videogame, for losing one match! It's just game, **right? **Season 5 I fought my way to Diamond 5 (anything for the borders) :D
Today, it's 15th of March 2016, Season 6. And I'm saltier than ever. Start of season, played those 10 provisionals. Lost 6, that's okay. Ended up in plat 5, five divisions lower. I'm angry, but I think i can carry myself back to diamond. I HAVE NEVER BEEN SO WRONG IN MY ENTIRE LIFE. I played and played, with my friend's help I got to plat 2, my friend got promos to diamond. Then our our winstreak ended: now I'm plat 5 and my friend plat 4. We both are at 0lp. Thats over 300LP LOST!!! 300!!!! I'm very salty/negative/toxic player. I can play very good but I also get tilted very easily. I'm impulsive person, and it just makes me wanna bash something when those "mid or feed - i select both" guys always end up in my games. Or if not those, then the "i'm riven main"'s who won't play safe and wait for ganks if they die to first blood, ending up to 3/9. I try to play roles where I can manage and perform well, like adc or top. Still, most of my games end up in huge loses, like 11/39 or mega throws where my teammates gets caught 1 by 1, even when we had advantage of 15 kills or so. I rage even after a little mistake, for example: my jungle comes to gank, we almost get a kill but enemy flashes under turret. I'm about to write gj and turn back, BUT my jungle flashes under turret for that "ez kill" but ends up dying at lvl 3 and not even getting the kill. That's my limit. I'm shouting like hell and grabbing my mouse tighter, I try to relax but the lane is getting really hard and jungle "needs to catch up so no ganks for a while." More bad plays follow: enemy catches double kill from our botlane and they write "ups :P". Another limit reached. "WTF HOW CAN YOU SAY "UPS" WHEN YOU LET DRAVEN GET DOUBLE KILL SO EARLY??!?!?!? NOOBSSSS L2P!!!!"

Yeah, I'm that guy who you all want to report after game.

The game goes shit and chat is full of "report Stiffmeisteir" whining and then I look t their stats: 0/9, 5/11. But report Stiffmeisteir for flame, that's always the drill. And even if I don't flame and mute my team from the start, still I lose the games!!! I feel really bad about my situation, and I really try to improve my behavior. I've had 75 game chat ban once (in 2014), and that was a real eye opener. Ever since I've tried to act better in the game, but nowadays it's so frustrating to lose and lose and lose..... Bad habits are rising their heads again.

**So, my fellow Summoners, do you have any tips how I could improve my behavior and climb the ladder? I appreciate everything that'll help me. ** Stiffmeisteir, out!