I think you need to stop thinking in chapters, because writing short stories is completely different than writing a novel or chaptered story. You have to approach characterization, detail writing and plot development so differently.
I would recommend reading more short stories (Best European Fiction is a great series of books, and they're all anthologies of short stories). When I started reading more short stories, and seeing how authors tell their stories, it helped me.
My favorite creative writing professor always did this dorky analogy with a water bottle; a novel is the water bottle, and a short story is only the drops that fit in the cap. You've got to get down to the most important drops of an idea.
I write one-shots all the time. During projects, in-between projects. Sometimes they lead to something more, sometimes I'm satisfied with them just being one-shots. They're a great way to get the creative ideas coming out.
I would recommend reading more short stories (Best European Fiction is a great series of books, and they're all anthologies of short stories). When I started reading more short stories, and seeing how authors tell their stories, it helped me.
My favorite creative writing professor always did this dorky analogy with a water bottle; a novel is the water bottle, and a short story is only the drops that fit in the cap. You've got to get down to the most important drops of an idea.