Working on the assumption that the parenthetical clause is to be included, one and two are good conversational ways to say it. Strictly speaking, 1 does not convey the message, but in conversation the meaning would be inferred. 3 is not a good sentence; I am not sure if it is grammatically valid, but it is extremely awkward. I believe sentence 4 is valid, but would not recommend it, as it sounds odd.
If you wanted to make the sentence shorter, you could drop either "of where I am" or "right now" (but probably not both) from sentence 1 and it would still be natural. You could drop either or both of these phrases from sentence 2 and it would be fine.
If you wanted, you could combine sentences 1 and 2 to make "Step B is way too far ahead of where I am now," as another natural way of phrasing it.
You mentioned idiomatic expressions; there is one that illustrates exactly what you are describing, but it's usage is kind of trickey:
"We (or I) will cross that bridge when we come to it." (many people use "get" in place of "come")
This is great as a response to a query ("what are you doing about B?" "I'll cross that bridge when I get to it."), but relies on the pronoun "that" making sense in context; as such, the preceding clause or sentence needs to make clear what "bridge" is being crossed.