What is the wear limit for tires?
Yes, there is, but it is not by regulation. It is in Advisory Circular 20-97B.

For example, section 7 would apply to most of your pictures:


  (7) In-Service Inspections (Operator).
  
  (a) Tread Damage Removal Recommendations. Tires that exhibit any of the following characteristics symptomatic of damage should be removed from service:
  
  
    (1) Cracking and/or cutting in a tread groove that is undercutting material adjacent to the crack or cutting that has lifted or can be lifted.
    
    
      NOTE: Do not probe cuts or embedded FOD when the tire is inflated.
    
    
    (2) Undercutting in a tread rib.
    (3) Transverse cracking in the tread that is visible at the surface and shows progression along an angular path down into the rubber.
  
  
  (b) General Tire Removal Recommendations. Tires with any of the following conditions should be removed from service:
  
  
    (1) Sidewall cuts that penetrate the outermost structural ply.
    (2) Internal separations characterized by bulges or distortions in the tread casing or sidewalls.
    (3) Heat or slippage evidenced by reverted or charred rubber above the wheel flange.
    (4) Tires worn or flat-spotted to the outermost casing ply (bias) or outermost belt (radial).