What men were left to fight in the War of Wrath?
 

What men were left to fight in the War of Wrath with the host of the West? I mean, the men of Hador(Marach) were enslaved, the men of Beor were basically all gone, and the men of Brethil were quite dwindled.

This is all that is said of the role of Men in the War of Wrath:

"And such few as were left of the three houses of the Elf-friends, Fathers of Men, fought upon the part of the Valar; and they were avenged in those days for Baragund and Barahir, Galdor and Gundor, Huor and Húrin, and many others of their lords. But a great part of the sons of Men, whether of the people of Uldor or others new-come out of the east, marched with the Enemy; and the Elves do not forget it."

I'm not exactly sure what men took part in the battle on the side of the Lords of the West, but it must have been a small number, as many were killed in the Fifth Battle. Besides, the Lords of the West had such a great host that they probably wouldn't need a few hundred or men.

Well, there was a large population of enslaved Edain in Dor-lomin (both Marachians and exiled Beorians) that would undoubtedly have risen up against the easterlings during the war. And though the house of Haleth proper (i.e. the family of Haleth) had fallen, there was still probably a decent population of the Halethrim at this point.