1. If the house is dried-in, the crawl space should be dry.
It should stay dry.
The surface of the ground (grade) should slope away from the house
in all directions.
Grade should be no higher at the wall of the house than the floor
of the crawl space.
Since folks make planting beds along the wall, the ground level
will rise over time.

2. Find out where the two pipe systems end.
You need to know that for maintenance.

3. 2x4s are not going to support much.
I should * think * masonry piers are needed.
Check the plans.
The poly should be lapped and fastened to the masonry at the edges.

4. Insulation placed when the crawl space is flooded is not going to do
well.

5..Building codes give * minimum * requirements for vent area.
Local climate, usual amount of soil moisture, and wind will
suggest what you need.
Check the Building Science Corporation web site for climate
specific suggestions.
6. Water in the crawl space is going to cause problems.

TB