How do I setup HA between two sites

I have one exchange 2010 server with the mailbox, CAS, and HUB roles.  We have about 200 mailboxes and almost all of them are accessed over Outlook Anywhere.  I have a new site (AD and physical) that I want to have as a backup / failover site for when the main site goes down.

From what I've gathered from internet searches I need to do the following:
1. Add 2 new exchange servers to the main site, one for the mailbox role and another for the CAS and HUB roles.  
2. Migrate and get rid of my current "all-roles" exchange server.
3. Add 2 new exchange servers to the backup site, one for the mailbox role and another for the CAS and HUB roles
4. Create a CAS Array between the 2 sites on the CAS/HUB servers
5. Create a DAG between the 2 sites on the Mailbox servers

My general questions:

First of all, do I have this right?
How do I configure DNS (public and private) for the servers and the email domains they serve?
How do I configure my outlook and mobile clients?
I have access to some hardware load balancers (pfsense, a linux distro for firewalls) would they simplify any of this for me?  If so how?
Should traffic between sites travel over the internet or over the VPN?

TIA for any help you might be able to provide

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J. Duke Rogers Communicore Technologies & Triangle Forensics