Well, the "general" age for a Yorkie puppy is 12 weeks old. If smaller, sometimes they wait until they are a bit older.
And a 6 month old that's 7lbs will probably grow a bit bigger than 8lbs, but not to much bigger. I'd estimate maybe 10lbs full grown? I think that sounds perfect in my opinion! I have a 14lber and he's PERFECT sized for me. He's still so small until I see him around a 5lb Yorkie, then he looks big, LOL. But he's so durable, doesn't get hurt easily, can be roughed around, etc... He's got the silver-ish color on his back but his legs/feet and snout are a tan/gold. He's only 8 months old though so he's still changing colors. I thought I'd be particular about color too but once you fall in love, it doesn't even matter

I keep him in a short cut, not the long hair.
As far as neutering, 6 months is a great age, before they begin marking, etc. Food is up to you really. My personal advice would be to stay away from anything with by-products, unnamed meat, corn, soy, or wheat. Jackson loves Innova.
I'm in Annapolis, MD, by the way! Cool to see someone else from MD