using Find My iPhone for missing phone if OFFLINE

hi guys.

my dad in another state has lost his iphone and i am trying to help him from another state. needless to say he is not so good with these things.

however, i HAVE previously set up find my iphone, iCloud backup etc and i have saved all his passwords for him.

the issue i am running into is that his phone is showing up OFFLINE.

so what i have done is to check the box that says PLAY SOUND and i have checked the LOST MODE and put MY PHONE NUMBER on the home screen along with a note about a "reward".

can anyone help me explain to my dad what is going on at this point and what the worst case scenario is?

1. am i correct in thinking that the phone battery is likely dead? if you call the phone it goes directly to voicemail.

2. is it necessary for the phone to have a live battery AND access to WIFI or can it have a good battery but no access to wifi to - for instance PLAY A SOUND?

3. if he cannot find the iPhone what do i do next?

A. have him go into the iphone store, buy a new iphone and then hook up his phone to ICLOUD and /download/ his data to the new phone?

B. then he (or i) go into his icloud account and ERASE IPHONE so that if someone finds his phone they can't get his info?

i am a little confused about a lot of this so it would be great to get some clarification. also i am going to have to walk him through this and his hearing is not so good so it is going to be a real pain.

thanks in advance for any help.

JJ