bandwidth usage for antivirus, vs, upgrade versions (excluding file backup)

1: *Pulls out the calculator*  The AV portion of WSA uses an average of 650k per day per computer for cloud communications, with a general range of 300k to 1.5mb.  So you're looking at about 58.5MB per month across three computers for the AV portion.
 
2: Specifically excluding cloud backup/sync, nothing in Essentials will increase the bandwidth use.  The current password capability of Complete uses about 20mb of bandwidth to install (one-time) and a trivial amount of data to transfer an encryped and compressed password payload anytime the toolbar is logged into or a pasword is added or changed.  That payload is generally under 2KB.
 
3: Complete specifically covers three Windows PCs and three Android/iOS devices separately.  There is no AV capabiliy for iOS though, due to limitations in iOS itself.  So three WIndows PCs and one Android smart phone, for example, would count as three and one, not four.
 
4: Partially.  If you are connected to a WiFi network at any location that does not count against a monthly cap, then it doesn't.  The definition files that are downloaded for Android's AV capability are trivial.  About 100K for the initial download and then incrementals of about 5-20k a week on average.  If you opt in to WARN data (Sending information to us regarding the threats found on your device as well as a the generic count of non-threat objects), that will only ever send across WiFi.  iOS uses no AV, so that is moot on that, as it's Browser and Sync only (Browser has about a 300-500 byte overhead on HTTP connections for checking the safety prior).  Control data for the AV Lost Device Protection on Android uses about 3KB per day at most and only in extreme circumstances.