Jim,

There isn't a need for flashing at all if you use treated or other
weather resistant wood, IMO.

Treated lumber will prevent the deck from rotting, but it won't protect the
house structure.

Any water that works it's way down between the ledger board and the house
siding is potentially a place for rot to start. If you have a good roof
overhang and caulk along the top, it probably won't see enough water to
matter. But, if this were on a wall fully exposed to rain, I sure wouldn't
want to risk it.

I've seen plenty of rot behind simple horizontal trim boards on a house,
and that's with an annual check of the caulking. Once a deck is installed,
you'll probably never look at the ledger again, or even have access to
recaulk it when needed.

I would still vote for a self supporting structure, not attached to the
house at all.

The deck should slope away from the house about 1" in 4'

That seems rather steep to me? The plumbing in my house uses that pitch.

Unless you are using T&G decking, most of the water will fall through the
gaps between boards anyway. And, a slope would be useless if the decking
runs parallel to the house.

Anthony