There is no roadmap and no clear answers to any of your questions. The answer will always depend on your personal circumstances, so the best advice is to keep learning, and keep asking questions until you understand the pros and cons of different approaches well enough in order to intuitively know what's best for your particular situation.
As for e-fund, people here keep anywhere from $0-a few years of expenses in an e-fund. The reasons behind those decisions are as varied as people themselves.
How much you put aside will depend on your job circumstance, how comfortable/uncomfortable you are with the possibility of having to sell equities when they're low, how focused you are on maximizing every dollar, what your cash flow needs are, what your tax situation is, etc, etc.
When you are 100% invested, it's not like the funds aren't available, there are just certain consequences to cashing them out. Assess those consequences, plan accordingly.