Hi Rick
Welcome to the site, I've been here about three years and all this sounds common to me.
Personally as soon as chat gets weird I disable chat straight away, if its been bad I'll report at the end of the game.
As for someone stalling in a lost position - if there is only one possible move like the queen you mentioned earlier then pre-move is a great way to tackle that - practice in a friendly game. You only get one candidate move in live chess so as long as you're certain it's a great option for those who stall for ages then randomly move at the last second hoping you've gone away. You can nip off to make a cup of tea safe in the knowledge that when you come back you've won either way
I've played over 1500 games on this site in the last two years and never been trolled or mocked in the game chat. As for childishness and pettiness of people who can't take defeat and abandon or time out the game, yes had those in abundance. I just smile when that happens because at the end of the day I'm the winner and they're the loser. Let them drown in their spite. And remember, a huge percentage of members on here are indeed children.