No, he's more like a couchsurfer that wants the legal tenant on whose couch he is staying to provide cleaning services, indefinite rent-free residency, and to allow him to do things that violate the tenant's lease.
But not a squatter, because he has permission, for now.
That's absolute bullshit. Anne Frank was hidden inside an annex of her father's company, BY her father Otto Heinrich Frank, a former German officer decorated during the 1st World War. HE told her how he planned to hide her.
Nothing to do with squatting, and frankly (no pun intended) you should be ashamed of yourself for suggesting otherwise.
No and no. This is the civilian world. An embassy is an outpost of a civilian government. Despite all the spycraft associated with them, they are not military outposts and government cannot conduct military operations from them. They are armed only enough to defend themselves.
He is also definitely not a squatter. He was invited in. Squatters by definition enter without permission.
Where "adverse possession" aka squatter's rights exists, one much stay without the permission of the owner. A potential adverse possession can be avoided by the landowner giving permission. That stops any running clocks as the possession is no longer "adverse" to the rights of the owner.