how to add a REverse PTR Record on Amazon Route 53?
Solution 1:
If that address is your elastic IP, then you can submit a request for a reverse DNS record.
RDNS Request
However, I also find it odd that their own DNS service (Route 53) doesn't provide easy Reverse entries for IPs your account currently holds.
Solution 2:
The zone for reverse PTR records belong to whoever you got the IP address from. Contact them and have them add a PTR record for you.
They might be willing to delegate the PTR record to you. In that case you will need a zone like X-30.254.144.168.in-addr.arpa.