Here's some photos of problem areas of my deck and I'd like insight on how to fix.

Issues: splintering deck boards, warped deck boards, splitting/cracking deck posts, developed narrow board spacing, pine needle etc. debris stuck in board spaces and edge. Related: proper cleaning and treating. Sanding? Removal? Cover with an outdoor rug and some patio furniture? :-P

Upper deck splintered board:


Upper deck splintered board next to house:


Cracking corner deck post (this one shows the most severe damage):


Top of cracking deck post, mold (bird poop also):

(I have some decorative wooden post caps that I've been meaning to stain and install for the past couple of years, but I'm sure I need to properly clean and treat the top of the posts before I top 'em off).

Splitting deck post and railing:


Splitting/warping deck boards, pine needles etc. debris in spaces between boards (some areas even more severely upturned):


Regarding the pine needles and such between boards, I've just been laboriously picking at them with tweezers, using a knife to poke through, toothbrushes (including the kind for braces) to clean and remove. What do the pros do? Leaf blowers, pressure washers and compressed air can't thoroughly deal with this. I don't want to damage the wood any more than I'm already doing with trying to wedge a non-serrated kitchen knife down through, but some boards have just become too tight to do that, but I can still see a pine needle in there.

I recently bought a 5 gallon bucket of this Olympia Wood Protector (it was half off since there was a puncture in the lid). It's advertised as a stain and sealer. Not a great warranty, but I'm just really trying to fix this place up to make it salable. It at least seems better than my previous method of mixing various shades of leftover exterior stain to make enough.

Note: I didn't build the deck, my parents did, when they built the house in '88. In the beginning the deck was regularly cared for, but life comes along, and long story short, the last 10 years or so have seen long stretches of abandonment with intermittent shoddy maintenance (re: me staining the deck with a mixture of various leftover stains because I'm cheap; hiring supposed professionals to paint the trim of my house who felt it ok to paint over mold, mildew, pine needles, cocoons, leaves of shrubbery touching trim, etc. Moral of the story, get references of the references, since we eventually found out they were ex-cons who used their buddies as fraudulent references). These recent trim painters also got white paint on the wood stained deck and siding: is there a gentle way to remove this without staining the wood?

I see there's some similar earlier posts, but I thought it could be beneficial to have a critique of my particular issues, and with product recommendations since new and sometimes better products become available or old manufacturers change formulas, etc. If there's any threads you'd like to direct me to I'd appreciate that as well. I see responses concerning post cracking as being normal and not problematic, but I posted my photos to see what others thought. The deck makes extremely loud sudden noises occasionally at night in the winter months, I'm sure due to ice and whatnot, but I wanted to know if I should do something about these large crevasses in case actual damage might re