A year and a half on. The bitnami docs don't make it easy to figure out how to do this.
Best thing to do:
1. Disable apache, as above. Works great.
2. Install pm2: "npm i -g pm2"
3. Set pm2 to always start its daemon: "pm2 startup"
4. Load and start your app: "pm2 start myAwesomeApp"
5. Save the pm2 config: "pm2 save"
Now, pm2 will always start your app on server start. Hope this helps someone.
If you ever want to disable this auto startup, "pm2 unstartup"