I'm not an Inaros expert but I'm fairly certain it does not. The dispel from Scarab Armor only replenishes Inaros' health and the Scarab Swarm thing only heal Inaros and allies. However, I could be wrong, it would require some testing I suppose.
It does and it doesn't. Since Inaros is my most used frame I can tell you that scarab swarm DOES heal defense objects (be it a crypod or an NPC) and mobile defense objects most of the time. The thing is that it does not work every time. I haven't been able to pinpoint the reason when or why it does not work. It does not seem to depend on the tile set, neither do sortie missions have any influence on it. So it seems to be glitchy - either by not healing although it should, or by healing although it shouldn't.