Muzzle: Try this https://www.kbchorsesupplies.com/wire-mesh-muzzle-with-headstall-horse.html . Put it under the halter and make the throatlatch on both tight. Greenguard is not adequate.  Return it.

Standard fly repellants do not work against Culicoides. Try a heavy application of Noxzema.
--
Eleanor in PA

www.drkellon.com 
EC Owner 2001