How to finish pressure treated lumber gets asked here a lot and I've read through all the threads and could still use some help.

I have a garden shed in SE Wisconsin. The floor is pressure treated plywood and there is a ramp that is pressure treated 2x4s. It's newly built.

I've read that new PT is probably 40-50% moisture and not suitable for finishing right away.

The builder got the PT from a big box retailer and with my moisture meter, I'm measuring about 20% - I'm guessing it "weathered" at the retailer then?

I'm using a Cabot Problem Solver Oil Stain primer which says it is suggested for pressure treated lumber and its main stipulation is moisture should be 15% or under.

Appearance wise it still looks rather green, but the moisture meter says not so wet.

So really three questions -

1) If it's below moisture levels, am I ok to go ahead and coat or should I still let it weather?

2) Since it was built already, I can only coat top and sides of the floor and ramp - not bottom. Still good idea to finish? I know ideally all sides, but can't do it this time.

3) I was planning to use Cabot solid arylic stain as top coat on the floor with the intent there being to tide me over until I can afford to do some FastDeck flooring. I was going to mix in some sand for the ramp. Good/bad ideas?