Answers ... my opinion only ....

1. Yes you use the total projected area. You might be able to apply a reducing shape factor (Cd), depending on the Reynolds number.

2. Ignore the small contribution to strength that the insulation may have. It is common to use yield stress as a sustained stress limit for blast.

3. Deformation depends on many factors ... like what the cladding is made of. Just ignore deformation.

4. Values of Cd are logically based on a cylinder. DAF is nothing to do with shape. I've never seen the shape of deformed cladding addressed.