I’m actually not super interested in the character, but I like a challenger.
First, put him through the ringer - discharged, experience the worst that’s happened to vets in America (if you know, you know), sometimes directly, sometimes not (occasionally you can just use a villain as allegory). Next we can do some “low hanging fruit” type stories that are obvious like temporarily depowered, refuse a job back in the military with Eiling, etc.
Before I get too far off from his “down to earth” stage he should deal with some bank robberies that are all vets, since that’s really popular as a trope these days.
I’m personally not a huge fan of most modern wars or the manner of US involvement even when it does happen, so re-integrating there will be a challenge. But I know I have to do that because the next writer totally will - status quo is god ofc. So what we’ll do is have a UN task force that the good captain joins and does some “ethical interventions”. So instead of (for example) bombing everything, maybe a country whose war stems from food scarcity could see Atom’s team distribute food. You could play with your molecular manipulation powers that Atom apparently has to literally magic in food.
Anyways that’s all I got.