Is it possible to synchronize the IDSM configuration between the two IDSMs installed on the two independent chassis.
I think it should be OK to do it this way, but just make sure both IDSM's have a diferent hostname and IP Address.
Also if you added the Sensors key to some device (for example during blocking) make sure you add both sensors to the blocking device.
No. You have to either do it manually or use Cisco Security Manager AFAIK.
All customers should push Cisco to give 'real' failover/high avail. support.