#3 - I did the same in terms of building a brand new trigger assembly without removing any parts from my stock assembly. I used A&S trigger guard, FFT upgraded trigger kit and springs, an upgraded safety, and all the rest I bought new Benelli OEM parts. I published a list of everything I bought on a post in this forum if you want to search. it was fun finding all the parts and building a trigger assembly from scratch.
#1 - I ordered CC tube, follower, and spring. I just received it and haven't installed but the quality looks great.
#4 - Benelli parts announced another presale coming soon. If you email him sometimes he will give a clue on timing.
Enjoy