You don't need another SSH host, your mac can use SSH, and on Windows you'd use PuTTY
To copy a file from my mac straight to a Linux EC2 this would be the command:
scp -i "/Users/wimdecorte/wim_ets_15.pem" ~~some file goes here~~ centos@largepinguin.ets.fm:/home/centos/
I'd stop after the pem, drag and drop the local file into Terminal and then type (or paste the rest)