So you are current with this the problem:
08:20:21 socketio.1 | /bin/sh: 1: /usr/bin/node: not found
I think you can safely ignore the WARNING notes.
Maybe just a path problem?
frappe@ubuntu:~/frappe-bench$ whereis node
node: /usr/bin/node /usr/include/node /usr/share/man/man1/node.1.gz
frappe@ubuntu:~/frappe-bench$ node --version
v6.13.1
frappe@ubuntu:~/frappe-bench$ npm --version
3.10.10
I suggest this first:
sudo apt-get update
sudo apt-get upgrade
then run this:
bench setup requirements