.my therapy wouldn’t change how he will be impacted in the school and further..
Yes it will.
Not that you going through therapy will directly change the way his teachers and classmates treat him, but it will definitely change the way you see this whole matter, the way you react, and the way you respond to your son. That in turn will give you the ability to be his ally in a meaningful way.
When he has problems in school, if you're still stuck in this helpless, feeling guilty state, you won't be able to help him. If anything, you'll make his problems worse, because your emotions will overwhelm you and he'll feel he has to support you. But if you have therapy and work through this, you'll have your own emotions taken care of, and you'll have the bandwidth to give your son emotional support and to fight for him if necessary.
Farther down the road, if he's grown up with your support, he'll have the ability to navigate life, disfigurement and all. If he hasn't had your support, he'll be crippled in his ability to make his way.
You couldn't prevent his accident, but you
can prevent your response to it from causing him more problems.
Looking back to the horary chart, your significator is Saturn, it's in domicile, and it's tightly trine your son's significator. That says the real power in this situation is in your hands, and you're in the best possible position to support your son, if you use that power. Not the doctors, they've done what they can. Not by regrowing his fingers, that's impossible, and the chart is clear on that. But by strengthening yourself.
Edited to add: On a reread of your post, I see he's only lost two fingers. That's not an insurmountable handicap at all. It might not even hinder his ability to do anything, just make him look a little unusual, and that's easy to get by. A college friend of mine had a couple of missing fingers from an accident, and he found it fun to be so unique looking. Nobody ever gave him a hard time about it.
Your son might even be able to use that to his advantage. If people give him trouble when he's older, he can hold up his hand and say, "See this? I got that dealing with a smart a$$ like you. You should see the other guy."