muffs
You seem to be having trouble with compound words. Which thing do you have more of - ears or muffs? You don't have ears muff because it's not the ear that's the thing, it's the muff - so you say two ear muffs.
That is the correct spelling of the plural noun "muffs." The use for "ear muffs" is also spelled "earmuffs."
Yes, the word earmuffs is one word, virtually always used in the plural.
There is no plural form. Do and Do not are verbs
The plural form of him, her, or it is them. (objective pronouns)
Bridges is the plural form of bridge.
The plural form of "is" is "are."
The plural form of "I" is "we."
The plural form of "was" is "were."
Yochanan Muffs died in 2009.
Yochanan Muffs was born in 1932.
"Groceries" is the plural form of "grocery."