vCentre Install questions.

Experts,

Couple of vCentre/ESXI questions.

1. On the single sign on part of the vCentre install, do I use my AD Domain name or something entirely separate to this, like @vSphere or similar? In other words, what should the domain be, the AD domain on a compete separate entity?

2. If f I was to install ESXi on a second server, would I then need to install vCentre on this device  as well and then add them both to the datacenter? Or is installing vSphere on one box all that is needed and then you add ESXi hosts to the datacenter from within vCentre?

3. On the DNS server, should i create a host record and add the hostname of the ESXi server? Or is it best to create a new zone with the SSO domain and then add in the ESXi host as an A record? And then do I add a new reverse lookup zone and what type of record, if any, do I create here?

How many CPUs should I assign to vSphere  - the default is 2 (I have a total of 8 virtual processors). Whats the recommended CPU allocation?

Thanks!