ADFS internal and external users

Hi,

I've been trawling the 'net' for an answer and diagrams (including network ports) to show how to configure a scenario for both internal and external SSO/ADFS 3.0 design.

I understand I need an internal ADFS server farm (which can be used for internal SSO access.
I also understand I need a WAP server farm in a perimeter network/DMZ for external users.
A public SSL cert wil be used: e.g. adfs.company.com
We'll use DNS internally, internal domain is company.local so i'll add a zone from company.com with an a record of adfs.company.com
We'll use a host file for the WAP servers in the DMZ
The WAP farm servers will obviously communicate with both external clients and the SaaS provider.

How will the internal ADFS communication work for internal users? Does this traffic go out via the WAP server route or will it require it's own access to the SaaS provider?

Also, (sorry I know this is another question)
Is is viable to setup two separate ADFS farms in two locations and use something like route53 to route to site two if site one goes down?

I'm also assuming that port 443 is used for all server and client comms.

Appreciate any help on these questions.

Thanks,
Andy