Hugs and prayers for poor Sky!

Ask the vet if there is a small dose of antihistamine you can give him meanwhile. And my guess is that since he is sneezy and there is goop, that he is a bit drier than usual, so his drinking more water is a good thing.

If your bathroom is small, you could close the door and run the shower hot - 'steaming' might help him, or a vaporizer with Vicks where he usually sleeps.

Will be keeping my fingers crossed for Friday.