I have had success recovering services a few times. I don't know exactly what the one item that works each time, but here is my typical recovery steps:
1. Set all certificates to None using Server.app (wait till it completes).
2. Repair disk permissions.
3. Restore /var/pgsql from the last known working instance.
4. Restart 2-5 times, by this time pgsql should be starting on its own again, and your services should have recovered themselves.
5. Make sure DNS service is running with Server Admin.app, seems to be required for mail and wiki to startup.
6. Choose the correct certificates for each service again.
7. Reduce mail security required for incoming SMTP connections to allow incoming mail with Server Admin.app.
My issues are all typically spawned from pgsql not booting, or rather claiming to get a shutdown request immediately after starting up. Once I have it running it stays running until I reboot or install updates again. Its been up for over 20 days now.
Good luck! I really hope that Apple fixes all these issues in the next update... it would be nice to be able to reboot it whenever and have reliable services. I still have yet to get the profile manager and podcast manager running. They seem to be the cause of some failures when I first tried them out.