Hi there,
No 1 - it's not really a good idea to run the CPU cable behind the graphics card as it may unseat the card during operation, an extension would solve the problem, something like this>>> http://www.amazon.co.uk/BitFenix-8-Pin-EPS12V-Extension-Cable/dp/B004J3P8SS/ref=sr_1_1?ie=UTF8&qid=1436353736&sr=8-1&keywords=bitfenix+extension+cable
No 2 - 8 pin connector or 4+2 pin connector for what???
No 3 - Don't worry about that tab it's not really a big deal, you can correct it if you want to but leaving it there wont cause any issues, if you do use the HDMI imput in the future you can correct it then or just bend that piece out of the way.