I actually had no problem with this episode. Kirito being at a disadvantage against a weapon wielded by a person who more or less was designed to kill him is more than believable, and while he could have bought two swords (price was 150k, if I remember right, and he won 300k from the game), that would have neglected armor and a range weapon in a gun-based game. Did no one else pick up on the "hospital" and "medicine" mention from the previous eps? I found that suspicious, and then as soon as I saw the guy's obsessive nature in GGO after the playground scene, he was on my list of suspects. I don't think he snapped from rejection, I'm pretty sure he was well broken before, so his insanity was not unexpected or out of character for me. The rape/murder was stopped actually I think a little past what you'd expect of a series geared for younger crowds, and yes while a full rape may have been a super turn-on for hentai fans, that's something for fan fiction rather than public TV.
As for Kirito coming to the rescue, it would not surprise me at all if he reconsidered momentarily Death Gun's parting words and straight up charged over to Sinon's house while keeping Asuna in the dark probably for her own safety. Or he may have left her instructions to call. Based on that, and him saying Sinon's house was near the hospital, he could definitely reach there before police, and it is just like him to do so.