The room above has a significant tilt, which leads me to wonder if the tilt is related to the dysfunctional support system.
Which problem should I deal with first?
The trash
the supports
the dirt floor
If you want a class A job done here.
OUTSIDE
1. Check all gutters for flow and down spouts far enough from the foundation so water issues are present for sinking.
2. Check grade around that sunken corner so water doesn't sit there
INSIDE
1. Remove rubble, But before that use it to re wall up that one side which appears to be blowing out and possibly allowing heavy rain water to seep into the crawl space. That water movement will cause the sinking you have over time.
2. Check sister joist ,I see scabbed Joist on the side of the old joist, which indicates the old are splitting/cracked and that's where the post are.
3. If some of the old joist are sagging and cracking then that needs addressed so lets hit them all
4. Pick out the center of the crawl space. In both directions this is where the first New center Pier will go. Scrap to virgin ground so you can form and set a 24"x24' area poured with concrete.
5. Form up that center pad with 2x6. so we end up with a 24"x24' square pad out of 2x6 to get our concrete 6" deep. Use 3/8 rebar in the concrete pour.
6. Make two more of these in that same center line ( Long wall perpendicular to joist) at each end of the inside foundation
7. Pour pads let cure.
8. lay 8x8x16 block jambs side by side on the 3 piers.
PIERS HEIGHTS
This is where it gets a bit tricky to catch the joist evenly. String line that center and keep the line down form both end joist bu wall equal distance. Go to the most center joist and measure down 10' this is where the center Pier block height should be. Use that center Pier as a bench mark to level the other 2 piers.
After the piers are laid level to each other you can use tripled up 2x10s to make a beam to set on top of those piers. The 2x10s can be cut so they meet in the center Pier. Set 2x10 beam From there you can build up shims/boards to catch all the floor joist. Before you put the shims in Nows the time to cut sister floor joist and screw them onto the old joist. They also can be cut in the middle where those shorter lengths meet on top of the new center 2x10 beam. This will greatly help installation to work them on to the ends of the old joist.
There are options her that you can use a bottle jacks and jack up the sagging center joist to level out some of the dip. And them add your board shims above the 2x10 to lock it in.
This I'm sure sounds like a bit extreme project but it address ALL the joist and properly sistering the old. It also gives you the option to re bottle jack another year to take more center dip out of the floor.
The extreme here is jack up the one corner but that will only hold if the foundation stops sinking. By all intense and purposes if you have proper drainage away from those walls and patch up the wall(S) so surface ground water doesn't run into the inside things should be fine. Even though the basement doesn't get water or not reallying seeing it in the crawl space doesn't mean some is seeping in form that collapsed corner, which I feel is the culprit here
The finial thing here to do is lay a 6mil plastic on the dirt floor for a moisture barrier. And to spray foam the joist bays for insul