I interpret the categorical imperative differently than you do. I agree that one of the most straightforward readings of it seems to be advocating for everyone to be lawful stupid — "lawful stupid" is the perfect phrase for how I first interpreted Kant when I'd only heard about fragments of his ideas.

I find this lawful stupid conclusion to be a useful step towards thinking about the categorical imperative in a useful way. Sort of like "what would need to be true in order for this to make sense?".

For example, in your second point, I think the categorical imperative might ask us to "zoom out" and consider why we're in a situation where we have to make a bad choice. After facing such a choice, people may ease their conscience afterwards by convincing themselves that the bad thing they did was actually good because it prevented a worse thing. I feel like a more Kantian response would be to let oneself be uncomfortable with the small bad deed, in order to understand how to prevent that from being necessary again in future.

I think that zooming out to get more context is often the solution to lawful stupid. Your final example resonated with me because that situation is something I've struggled with a few times in my life. When I have cut harmful people from my life, it was because it was clear that they were hurting me to an unreasonable degree, and diminishing my capability for kindness. One of those times, I didn't so much decide to cut someone off, more to just spend my energy where it would be more useful, which led to me cultivating a network that helped me to realise how toxic that friendship had been.

Personally, reading Kant has led me to take a more "ecological" view in areas like this, where I consider myself as one small part of a much wider system. I haven't read Kant in too much depth though, so I'd appreciate any input you might have — I'm very much a scientist dabbling in Philosphy, so I have a lot to learn. In particular, I'm curious about if there's an alternative philosophical framework that you find does work for you.