Is the words slave and act proper nouns?

No, the Word 'slave' is a common noun, a Word for any slave anywhere.

The Word 'act' is a common noun, a Word for any act of any kind.

A proper noun is the name of a specific person, place, thing, or a title; for example:

• 'Dave the Slave', influential nineteenth century potter whose pieces are highly prized today.
• Act Drive, Iowa City, IA
• Slave Lake, Alberta, Canada
• Act Tower, Hamamatsu, Shizuoka Prefecture, Japan
• The Fugitive Slave Act, 1850