I have some trouble answering your question, chiefly because my definition of "expert" is approximately synonymous with your definition of "Level 2".

Or, to put it another way, do you think that, given enough time, but using only your present knowledge, you could teach a reasonably-intelligent layperson, one-on-one, to understand complex topics in your expertise, teaching them every intermediate topic necessary for grounding the hardest level?

"Enough time" would be quite a long period of time. One problem is that there are a lot of textbook results that I would have to use in intermediate steps that would take me a long time to derive. Another is that there are a lot of experimental parameters that I haven't memorized and would have to look up. But I think I could teach arithmetic, algebra, geometry, calculus, differential equations, and Newtonian physics enough that I could teach them proper engineering analysis.