How to escape in yaml the correct way?

On CentOS 7 I am using cloud-init to spin off a droplet using the DigitalOCean API which requires yaml formatting.

I got most parts working fine, but struggle on escaping the commands running at 'runcmd' below:

#!/bin/sh

set -e     # Stop on first error

curl  -X POST http://ift.tt/1miSDzD \
-H 'Content-Type: application/json' \
-H 'Authorization: Bearer '$api_key'' \
-d '{
"name":"'$droplet_name'",
"region":"'$region'",
"size":"'$size'",
"image":"'$image'", 
"ssh_keys":'$root_ssh_pub_key',
"backups":false,
"ipv6":false,
"private_networking":false,
"user_data":"
    #cloud-config

    users:
    - name: SomeUser
      groups: wheel
      shell: /bin/bash
      ssh-authorized-keys:
              - ssh-dss AAAABBBBCCCCDDDDD...

    runcmd:
    - sed -i -e '$aAllowUsers SomeUser' /etc/ssh/sshd_config
    - sed -i -e '/PermitRootLogin/s/^.*$/PermitRootLogin no/' /etc/ssh/sshd_config
    - service sshd restart
"}'

The errors I receive are:

curl: (6) Could not resolve host: no
curl: (3) [globbing] unmatched close brace/bracket in column 63