my opponent refuses to accept the draw. it's king vs. king and nothing else left on the board.Am I to continue this game?

Just keep playing moves and offering a draw, either your opponent will get bored (or will otherwise time out), or Richard will notice, and force the end of the game manually.

Your opponent may be higher rated, but he certainly ain't very smart.

Threefold repetition is automatic draw in this site, so just take the opposition and wait for repetition.