In answer to your Point 1 - no I can't see a way to tell auto-arm to do one or the other - it's just full arm and full disarm on the automated option.
In answer to Point 2 - How are you arming the system? Are you using your phone, a remote or a tag reader?
I think on the remote button there's no option - and using the tag reader in 'standard mode' rather than 'simple mode' it does ask you to confirm which areas you want to arm, but again I don't think it gives you the choice of 'Stay' or 'Away'.
I think the only option of choosing 'Stay' or 'Away' is through the phone app on a manual adhoc basis rather than being able to automate it in any way. (Will wait to see if anyone else is aware of any workarounds).
One suggestion might be to set up 2 zones in the house (So 'House Perimeter' and 'House PIR' for example). You then have perimeter protection on one zone, and PIR's on the other zone.
Then you can auto arm/disarm the perimiter zone each day and night as per your requirements, and then manually set the PIR's if you go out and leave the house empty,