Script:

I would probably add logs to the code to debug and to verify everything. Maybe considering adding:

set -x

You could dryrun suspend and check if something is blocking suspend

sudo /usr/bin/systemctl suspend --dry-run

Work your way from there

Questions:

• Is it not suspending because I'm doing this over ssh?
  

Not really sure about that please read this before implementing. But you can edit /etc/systemd/logind.conf

HandleLidSwitch=ignore
HandleLidSwitchExternalPower=ignore
HandleLidSwitchDocked=ignore
IdleAction=suspend
IdleActionSec=10min

• Is it because systemctl suspend requires a password?

Since you already configured user drew to not need a password this souldnt be the problem.

• Is there an easier way or another tool to achieve the goal I am after?

autosuspend (Note: Its also open source)

If anything is unclear, misleading or if you have further questions please let me know :)