I have no help with you questions, but I wondered if you've heard about Petzlife? It's a tooth spray or gel that softens tartar making it easy to remove with a regular toothbrush. I've heard some great things about it, and many of YT members highly recommend it. It might be worth using for a month or so to check it out. Here's a link.
http://www.petzlife.com/index.html In sixty days there's a dramatic difference, and maybe he won't need the cleaning. You can find it cheaper than this place if you do a google on it.