1. Yes, you can use replica mapping option
in the job settings to do that.
2. Are these vCenter Server independent from each other or you're running the vCenter Server in a linked mode? Anyway, it is recommended to have a copy of your production infrastructure in the DR site. This would allow you to do a seamless failover. Running the secondary vCenter Server on the remote site is not a bad idea
3. In case of replication jobs, it is recommended to run the backup server on the DR site orchestrating all the jobs. Here is an existing topic for further reading > vCenter and Veeam replication to DR site
4. Yes, you can do that via this option > Specifying Preferred Networks for Data Transfer