Eeek!! I'm actually quite shocked at the pics, and that it sounds like you haven't yet consulted a vet or farrier about this. You need a good one of each of these professionals, *urgently*! (as you can't get one long ago before this prob was so chronic/acute, so...). You need to find people who are lameness/orthopedic specialists. Your donkey needs way more than what is in the scope of forum replies!
I cannot give anything specific just from these 2 pics, except to say he's in a rather desperate way. You say this red shows 'with even light rasping' so does that mean you have rasped into the sole at the ground surface?? You should DEFINITELY NOT do that! He probably had thin soles anyway.
Saw Walkin's reply & agree. I think he is seriously foundered. But the imbalance & extreme length of the foot shows that he has been suffering from mechanical issues for a LOONG time. So while it may be systemic laminitis as well(& regular grass hay & pasture is often too rich/sugary for horses, let alone donks), it is definitely at least exacerbated by incorrect trimming, and possibly some limb deformity that's influenced the balance - beyond the scope here to do more than guess, but at 10mo if it is that case, it's now beyond the scope of a vet or farrier to 'correct' with orthopedics.
I marked your pics to show... on the sole pic that the heels are quite imbalanced, and all in front of that red line at the toe is acutely stressed/damaged external laminae. And the pic of hoof on ground, while it's taken on an angle, so this makes the view inaccurate, my red lines mark the 'broken back' hoof/pastern angle, the long, lumpy looking toe and the long, crushed forward heel. Also marked that while there may be some stretching, the other hind looks, from this angle, to be reasonable, as to the hoof/pastern angle.