I'm not sure how you missed the big warning at the top of the uninstall-CFW page which tells you to not uninstall CFW
You can recover your savefiles if you want. Did you format your SD card? Because that's where the saves are stored.
Yes you can use ntrboot if you like
The movable.sed doesn't just contain the keyY, it also contains a carbon-copy of the LFCS_B ( https://3dbrew.org/wiki/Nand/private/movable.sed )
Are you giving out LFCS_Bs via direct link here?
EDIT: Actually, by giving out a movable.sed with a bad LFCS_B in it, it will mismatch with the LFCS_B...
tbh that's mostly the only games people care about, i don't think that many people cared about the obscure japanese games (they were certainly a minority)
it is odd that pokemon hasn't been put on the blacklist though
You find your CIA online on some website (can't tell you, you have to find it out yourself), download it, and then install it with FBI, simple as that.
The N3DS has an upgraded quad-core, over the O3DS's dual-core ARM11
ARM9 is never taken into consideration when in 3DS mode as it never runs anything userland related