Assumming that the hosts on DMZ and Network A are using the local MFE interface IP address as their default gateway then the only static route you should need to create on MFE is one which allows traffic to be routed back to network B via the "other" Firewall.
When creating the route the destination would be 10.0.0.0/24 and the gateway would be the external IP address of the other Firewall.
Any traffic between network A and the DMZ shouldn't require any additional routes as both are connected directly to MFE (just as long as MFE is either the configured defautl gateway or the router being used as the default gateway sends all non-local traffic to MFE).
As far as network objects are concerned, they are only really used in the access control rules. So if you want to create rules with restricted sources and/or destinations then you will need to create appropriate network object entries.
Whether you should created "Host" network objects is a different question. Host objects will obviously need access to DNS in order to forward and reverse resolve themselves to the correct IP addresses. So, success or failure is really down to how you have configured DNS and how reliable it is. Ultimately, when I was trained on this product back at version 5, I was advised to avoid using host (or domain) objects unless it was absolutely necessary to do so - use IP address object instead.
At the end of the day (as he always said) "If DNS breaks, then everything breaks!".