No it doesn't matter if it is the drake or the hen that is blue fawn. So yes, if you bred him to a grey hen you would get roughly half grey and half blue fawn offspring. In small hatches those percentages can vary one direction or the other. The 50/50 percentage is based on hatching large...
Blue fawn is simply the grey pattern with the addition of a single blue gene. Pastels for instance are the grey pattern with two blue genes. If you breed blue fawn to blue fawn you will get 50% blue fawn offspring, 25% pastel offspring and 25% grey offspring. If you breed blue fawn to grey...