This son has had a lot of trouble already. His first child was born when he was 16. He's also struggling through what may be the end of a marriage that he doesn't want to see fall apart.
It seems like he runs into trouble at every turn.
There have been suicide attempts in his past.
Whenever things start to go well for him, something falls apart.

He lived on his own for about 3 years before moving back in with my wife and me about a year ago.
I've got 6 children, but he's the one I worry about almost nonstop. My concern bothers him so I try my best to not show it, but I always feel so bad for him. He copes with his issues much better than I do. He's had a lot of counseling in his life and has learned strategies that make life's troubles easier for him to manage, but it still doesn't make it easier to watch.

So when he told me that his social security card was lost, I got nervous. After about an hour, I asked him if he'd mind if I joined him down there and he texted me the address.

I understand that appeal of just letting him sink, but my own parents weren't like that and I've never thought they parented poorly.
I've got a younger brother who is 2 years younger than I am. He was a total flop for the first 19 or 20 years of his life. he dropped out of school when he was in junior high. My dad wasn't sure he could even read.
He knocked up his 15 year-old girlfriend when he was 19 and decided it was time to figure out life. It was hard, but my parents helped him along the way more than most parents would ever help. My brother, with my parents' help, rose from the ashes and turned into a decent, successful person. He probably has a few million bucks in the bank now.
Without my parents' constant willingness to help, I fear he might have ended up homeless.

SO, I want all of my children be self sufficient but I also hate to watch this son struggle. He's repeatedly through his life shown signs that he believes no one cares about him. He had a step-father who beat him regularly. While we were in Maui, I learned that it was worse than I ever understood it to be. He told his younger siblings(from my second marriage) that they're lucky to not know what it's like to have a bad, mean dad who beats them. He then explained how awful it was for me to drop him off to his mom's house and getting body-slammed by his step-dad as soon as he walked through the door. He doesn't know why it never happened to his older brother. It was only him. He also doesnt' know why his mom usually didn't even try to intervene. Most of the time, she just watched.
He then tried to cover for his mom and explained that he talked to her about it in the last 6 months or so and his mom broke down in tears over it and apologized but what's done is done.

He doesn't feel like people love him or support him. I"m trying to fix a lot of damage done to him during his childhood by showing unconditional positive regard and providing him a safe landing spot no matter what happens. He is still scared to ask for anything ever because he thinks he's not worthy of anyone's time or resources. It's painful seeing such a terrible sense of self-worth in him

So yeah, I imagine I've failed as a father in much bigger ways than merely helping him find a wallet. I didn't take better care of him when he was a minor and it will probably tear me apart of the rest of my life.

I appreciate your wise concern.