1: do I need 16ply.
If your coach came with Load Range H tires, chances are good that that's what it needs to carry the weight. Consult your Owners' Manual.
2: do they all need to be balanced;
In my opinion, YES! Your tire/wheel assembly weighs well over 100 lbs. I don't like the idea of something that heavy bouncing down the road when it could be rolling down the road! Your drivetrain will thank you.
3: anyone ever used "Counteract beads" for balancing?
I've used "Dyna-Beads", which is a similar product. They worked well for me.
4: does anyone have a suggestion for this size
Now you've done it! You can expect responses ranging from, "Get the cheapest tire you can find." to "If you don't buy Michelins, the world will spin off its axis and it will all be your fault!" Buy what you're comfortable with. Some of us have no problem riding on tires from companies that that don't spend millions on advertising, while others can't sleep at night without knowing that they spent as much as possible on their tires. It's entirely up to you.