1. No. There is no way to downgrade 3.56+ consoles without a hardware flasher such as E3 or ProgSkeet.
2. If you go with ProgSkeet, you can use a clip... Not sure about soldering, but you cannot use the E3 flasher as the CECHG was the last 256mb NAND flash console that Sony made (after it came the 16mb NOR flash consoles).
3. I believe there is a section for that.
4. Downgrade/running updates will be difficult. Every time a PS3 is updated, the drive FW is also updated... A non-working Blu-ray drive would usually mean updates would not go through. If I remember correctly though, with MFW builder you can get rid of the Blu-ray drive checks/updates. When building an MFW (CFW) using MFW builder for a downgraded console, you will have to disable lv1 checks as well. (This makes it so the firmware is not checked whether it is higher than the firmware than the console had before the update).