What a lovely IRN. He must have received a lot of care from where you got him. I can only emphasize how bad a 2nd bird would be to add, especially a cockatiel. Even though my IRN is bonded to this cockatiel here, I've been told by avian vets and others that IRN generally will kill a cockatiel, and that I should even separate mine.
Those sounds seem like sounds of content, and similar to sounds mine makes when I'm petting him. You've only had him a few weeks. Give it some months, lots of love and care, and I think he'll be just fine.
When you said he plucks, does he have any bald spots? Mine grooms a lot and I do not consider that a plucking issue because his feathers are full and clean like how your avatar looks.