I am not sure I follow the questions so forgive me if this is not the right answers.
For pointer records in DNS, you will need to have a static ip assignment for a carrier to adjust pointer records on your behalf. But the reverse record is generally only needed when you host email on prem so it is not an issue in most cases. You seem to be wanting some kind of forward dns or host record on a dhcp account. For this you can use services like noip for that purpose.
the destination nat issue on a dynamic interface is not supported on the SRX. So if you need to do destination nat to internal resources you will need to get a static assignment.
Ok you have two options,
1) Configure DDNS (Dynamic DNS) so that when your non- statically assigned IP address is update the SRX will update the public DNS server which your new IP address assigned to your SRX from your ISP. With this approach you will have a DNS name like mySRX.myddns.com = 184.108.40.206, you will then load this DNS address into comcast or xfinity as your personal IP address, I believe they do support this approach.
SRX Dynamic DNS Configruation
2) Get a statically assigned IP address from your ISP.
With regards to your destination NAT, as long as you specify 0.0.0.0/0 as the destination NAT address it will not matter if your public IP address changes, you will also need to ensure you are not limiting the public IP address in a security policy.
Either solution will work well.
Actually ... I dont believe you would need any destination NAT configuration to make this work, so not sure why you would reference the 0.0.0.0/0 IP in any zone/policy/nat? Dont understand that part.
Correct, if you need to configure NAT with a dynamic address you need to use 0.0.0.0/0.
You also need a policy from untrust to trust configured correctly.
Thanks for the Kudo's, not sure what you were trying to say in that last post?