Have you configured Network Failover for the correct VLAN and IPs and confirmed there's no serial cable in place?
Yes, VLAN configuration must be performed manually on each device - I'd suggest in advance of a failure!
Yes, you need to ConfigSync manually each time you make changes. I'm not sure anyone would like it to be automatic, especially if a misconfiguration or typo kills a service on all your devices - removing the opportunity of a backout by failing over! Of course, I'm sure there's some people using iControl or tmsh scripts to manage this.