I don't want to rain on your parade but let's do a quick reality check.
From your first post you make it obvious that you are not very experienced in designing power electronics. I repeat what i have said several times in the past here and elsewhere: one does not begin with off-line power circuits, one graduates into them. With the skill level your questions demonstrate, only disappointment waits for you, or worse.
Point by point response to your questions would serve little purpose - my advice is for you to spend considerable time studying the fundamentals of power electronics and especially their dynamics. The key, really the sine qua non, is to understand the mathematical representation of the power circuits and their associated control and compensation circuits and transfer functions. You cannot _design_ something you don't understand - only cookbook solutions are available.
Once again, i emphasize that i don't want to discourage you from trying but do set more realistic targets initially, until you have achieved something that works the way you wanted it to, and then proceed from there. You doubt me now, i am sure but see for yourself if you can manage the following fundamental questions, with or without supporting documentation:
- create the steady state model of the most common switcher topologies - say buck, boost, buck-boost and derive their transfer ratios as function of duty cycle. (And i mean _derive_ not just look up).
-calculate the loss model as a function of duty cycle and individual component nonidealities (you wanted a good efficiency!).
-create the canonical small-signal model for the common topologies and from those, extract the transfer functions and then calculate the poles and zeros of those transfer functions.
-then derive the loop gain and phase loci that enable you to do a stability analysis to decide if and what kind of compensation is necessary to make your switcher stable under all conditions.
After that is clear, you can start looking into the PFC. Since you didn't want to use a ready made chip, you need to calculate the power factor yourself by designing the multiplier and a modulator that controls the selected switcher to maintain optimal power factor. Here several design tradeoffs need to be balanced and i promise you a 2 kW PFC device won't happen by trial and error.
By all means try your project, but please adjust your target initally much, much lower. If not, your project is destinied to join innumerable other pies in the sky.
I recommend this book if you can find it at a reasonable price somewhere:
http://www.amazon.com/Fundamentals-Power-Electronics-Robert-Erickson/dp/0792372700I'm not your mother so it is not my place to tell you what to do. So you do as you want but please consider the above friendly advice, not a hostile putdown.