Update Manager Implementation Best Practice

I am planning to implement the vmware update manager. Briefing about my infra

vCenter is managing 11 ESXi 4.1 hosts for my desktop virtualization which is running approx. 900 VDIs  and 4 ESXi 4.1 for Server virtualization which is running my db cluster and other 4-5 VMs. My connection server & Replica server are physical and vCenter is also physical. Now, I want to implement VUM for my virtual infra.

1. Should I install VUM on a seprate Server or with vCenter server
   
2. What the database size will be required if I assume for 5 Yrs
   
3. Ports requirement
   
4. Is VUM is mandatory for my infra because I have non persistent images & ESXi servers