Hi,
Note : I will try to address your SRM queries first and then we will proceed further on other questions
First let me understand your requirement here. You would like to have DR site for your two datacenter ( Two Sites ).
So first thing is you need Bidirectional DR solution ( Disaster Recovery Solution ) since currently you have production machine on both the sites. Correct me if I am wrong.
Now question comes, do we need to go with SRM and ABR ( Array Based Replication ) or vSphere Replication which is agnostic of underlying storage ( does not dependent on storage array unlike SRM-ABR )
Here is link to comparison between SRM-ABR ( Array based replication ) and vSphere Replication
vSPhere Replication comes as virtual appliance ( Linux base virtual machine ).
SRM ( Site Recovery Manager ) need to be installed on windows machine or along with vCenter virtual machine. Yes , you need separate SRM server installation on each site.
Here is quick FAQ for SRM I recommend you go through it , http://www.vmware.com/files/pdf/products/SRM/VMware-vCenter-SRM-FAQ.pdf
If VM is protected by vSPhere Fault tolerance , then it cannot be again replicated by vSphere Replication.
Yes, vSPhere Replicated VM or Array based replicated VM can be protected by HA ( High Availability ) if there is any ESXI host crash.
With regards to VDP and vSPhere Replication, I think it can cause problem if they are running at same time. ( VDP taking backup and VSphere replication replicating data ) , Let me check on this for more detail.
Regards
Mohammed