Prepping and Staining 25 yr old Pressure Treated Wood

Hi,
First, I'd like to say thank you for having such an educational site. I have learned a lot! Below is the information you requested.

State: New Jersey(Northern)
Sun: Full afternoon
Wood: 25 year old Pressure Treated Wood
Mold/Mildew - As I sanded, looks like there was some black strips of mold/mildew under the paint
Issue: Need to re-stain as the deck was peeling terribly

The original owner painted/stained the entire deck. We can not tell whether it is paint or stain but in either case it is a solid paint or stain and appears very thick.
After 5-6 years of living there, the paint/stain started to fail and peel terribly. We attempted to power wash it to remove the paint/stain with no success. We tried scraping, also without success. The peeling was so bad that when the deck was hot from the summer sun, I was able to peel some sections clean off down to the pressure treated wood (PTW). Since the deck is fairly large, we ultimately resorted to renting a drum sander a few weeks back. I sanded the deck using 24 grit sand paper. It was a lot of work but got 90% off. I will have to use a orbital sander to get the 10% that the drum sander could not get to because some of the boards are uneven. Here are my questions:

I plan to re-renting the drum sander this week (after I hand sand the remaining 10%)to go over the entire deck with a higher grit sandpaper, if need be.

Sanding
1) a. Do I need to re-sand with a higher grit sandpaper i.e., 36 grit or 60 grit? Note: The wood looks very clean now.
1) b. If I do need to re-sand, can I get away with doing only 1 more sanding or do I need to do more than one?
2) a. If I can get away with 1 more sanding, do you recommend sanding with a 36 grit or go directly to 60 grit or something else?
2) b. If I have to do 2 more passes, what grits do recommend?
3) From what I have read on this site, it looks like I should stop at 60 grit(i.e., I should not use 80 grit due to lack of absorption of the stain with higher grit levels) - correct?

After Sanding
4) Do I need to use both a cleaner and brightner after sanding or can I go directly to staining? Note: I don't see any mold or mildew since I shaved off a good bit of wood with the 24 grit sandpaper.
5) a) If I have to use a cleaner and/or brightner, which cleaner and/or brightner do you recommend that I use?
and
5) b) How long do I have to wait before I stain it?
6) Is power washing recommended instead of using a cleaner and/or brightner?
7) If it is recommended that I powerwash, how long do I have to wait before I stain it?

Stain
8) Based on your reviews, it looks like I should go with a semi-transparent stain to avoid peeling and ease in reapplying in the future.
a) Do you agree?
b) If so, given that I am dealing with 25 yr old PTW, how do you think a semi-transparent stain will look?

9) If so, it looks like I should either use the Defy Extreme Deck Stain or the TWP 1500 Series Deck Stain (due to NJ being a low-VOC state). I am leaning towards the TWP 1500 simply because it got a 9 for peeling vs. Defy's 8.
What do you recommend given all of the info I provided above?

10) How long after I apply the stain can I put furniture back? walk on?

I realize that I have asked many questions so I want to thank you in advance for any recommendations that you may have.

Thank you again!

LC