I do agree with your sentiment. I think it should be a more gradual shift to madness. That makes a lot more sense to me, and it’s how I always imagined it.
I liked that they are saying their name trying to maintain that last shred of humanity, but they present as more rabid extreme shifts. Like the ghoul that’s killed and cannibalized going from having fluent conversations and vivid recollections to screaming his name is a bit much…
I think they should be in a confused and disoriented state like in dementia, and they should be near totally nonverbal by the point they’re trying to remember who they even are. If it’s caused by an irradiated brain essentially rotting away, then they shouldn’t be able to articulate and be reminiscing at that point…