Given how you have phrased the situation, I don't think you or your wife are in a place to take on battles. Please take care of yourself first, take care of your wife; tell her to take care of herself first, and then to care for you.
Take the advice of others here that makes sense to you. But give that your grief continues on after 2 years of losing your son, I would, if I were you, pick the suggestions (like that of @throwawaylinux) that help you resume normal life; it's definitely not going to be the same normal, but it would be better than how you feel now.
I have experienced personal losses, and it has taken me years to come to terms with my life as it is right now. I'm not fully recovered from those losses, but after a lot of recovery, I now consider myself to be extremely lucky to be healthy, and have a very happy family.
I am in the Bay Area. I can come talk to you, and see if I can be of any help as you navigate this tough part of your life. Please do not hesitate to send me an email gurjeet@singh.im, or share your phone number in email.
Lots of love, and wishing you lots of strength.
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Addendum: Of course, the culprits need to be brought to justice; be it the person who did it, the people who let it occur, or the emotionless company that continues its operations as if nothing happened.
But bringing them to justice doesn't have to come at a cost as big as your and your family's mental health. I'm sure you've spoken to lawyers, but if not, please get one. I'm sure there are lawyers who will not cost you anything money wise, and agree to be paid after the settlement. I have personally never dealt with lawyers, so I cannot suggest how to evaluate them; but look for lawyers/practices that treat you with utmost respect, and understand the pain you and your wife are in.
Not getting a legal representation, or just accepting the other party's offer, even if they manage to make it look large for you, will make you feel bad later on. For an auto accident I was in, I dragged my feet, because the money other party's insurance company was offering was not significant for me, and my symptoms were manageable. So when the Statue of Limitations was about to expire, I simply accepted their offer; never engaged an attorney. Now, years later , the symptoms are very hard to manage, and I wish I had engaged an attorney to represent me.
TLDR: Take care of your and your wife's mental well-being, then engage a good lawyer.