It is a teleport effect, does not require line of effect, by the wording it doesn't even require line of sight. If something was said before his action he would have done something different. The rest of the party have worked together in the past so some amount of table talk is reasonable, but any planing with Darrian would need to be in character.
And the elemental can fit, it can fight, it would simply take penalties. A person takes up a 5' square, but we are not 5' blocks. The penalties are there to show the difficulty for not having room to move around and dodge.