Create Dynamic Distribution Groups Using Customized Filters

I am looking to create a new Dynamic Distribution List. 

Example: 
DL - United States Users (DLUnitedStates@chiquita.com) 

In AD we have the 'Office' field filled accordingly, which contains the attribute USCA___ or USIL (US,California,etc or US, Illinois,etc). 

I was wanting to try creating these using this command/script; 

New-DynamicDistributionGroup -Name "DL - United States Users" -RecipientFilter {(RecipientType -eq 'UserMailbox') -and (Office -eq 'USCA*')(Office -eq 'USIL*')}

Assistance here please: 

1. What needs to be added in that line so that only certain users can email to it, rejecting all others (i.e. The Helpdesk or Corporate Communications)

2. Is there a way to specify the SMTP address you want it to use? 

3. Is there a way to have it only add mailboxes that are enabled in AD so disabled mailbox user accounts wont be added? 

Thanks in advance everyone.