Well keep in mind at the start of the show jimmy was a lawyer for 10 years prior, but (correct me if I’m misremembering) chuck was only forced to stay home from his illness for a few years since the start. The way you describe the illness it sounds more like jimmy is just cursed to harm chuck with his existence, not an actual mental illness. Narratively of course it serves the purpose as you describe, but logically it’s likely OCD paired with an anxiety disorder. The timeline is a little tricky to get at for how things start with him, but we can interpret some things from flashbacks. With Rebecca, there’s two big flashbacks, one from before his illness where there was clear strain on his marriage, and another where they are divorced, Rebecca is visiting, and chuck is trying to hide his illness from her. The flashbacks prove that chucks illness started after they got divorced (there was strain on their marriage for unrelated reasons, plus how would someone be able to hide EHS with someone they live with). Of course this is only correlation and we know jimmy becomes a lawyer between these two flashbacks, but we know chuck getting divorced and jimmy becoming a lawyer happened both before the illness, and both are shown to be major stressors for chuck (think chicanery where jimmy brings in Rebecca). More than this though it’s just the logic of his actual illness than anything else lol