Note: PM2 own code quality is bad and cluster_mode is not production ready. I would not recommend to use PM2, anywhere. You have been warned.
How to use a different ssh port for PM2
Since pm2-deploy directly forward the host string to ssh, you can simply use:
"host": "HOSTNAME -p PORT"
inside the configuration file.
How to use cluster_mode in PM2
Make your app instances listen on port 8000 and pm2 will load-balance any request on 8080 to your app instances.