1: Bill from TLoU, as others have mentioned. Kaidan Alenko is another good example, in my opinion. One bad example, for me, is Mizhena in Baldur's Gate: Siege of Dragonspear, it's so awkward and out of place and so obviously tossed in for the sake of simply being there with little to no narrative purpose. Lena Oxton in Overwatch is also kinda strange as a concept, the characters sexuality literally has zero impact on gameplay or narrative as OW is a simple hero shooter with almost no depth.
2: Interesting question, but it's kinda hard to know since it usually makes little sense for characters to blurt out their sexual preferences in most settings. If it's subtly done and well written, I'm all for it. But most such characters are fairly stereotyped and shallow and often seem placed out mostly for representations sake.
3: Not really, but it seems there's a ways to go before writers can create good LGBT characters since the above mentioned problems persist.
4: No, I'm straight.
End of 2016 hardware sales:
Wii U: 15 million. PS4: 54 million. One: 30 million. 3DS: 64.8 million. PSVita: 15.2 million.