Yes, there are several modchips that can be used to hack patched and newer Switch units. These include the SX Core, hwfly series, and picofly. You can find these on AliExpress or other resellers.
It depends. Do you think you will always have your Android phone on your person and a USB cable? If not, then an RCMLoader might be a better investment. Also, I cannot recommend any videos because its going to depend on what you use to enter RCM which can vary widely from jigs to paperclips to aluminum foil. RCM also looks identical to a black screen so you won't be able to tell its successful even after watching a video.
The SD card reader is actually quite fragile on the Switch so its recommended to not use more than 1 SD card per console for fear of breaking it.
Did you download your patches from this
thread? If not, I highly recommend you do so as that thread always has the latest working patches.
That user you quoted hasn't logged on for 2 months so you probably won't get a response from him. Have you verified that your SD card is not fake?
The corruption is not rare at all. If you look around, you will find a plethora of threads about people experiencing corruption on exFAT. Even leading developers on Switch hacking highly dissuade against using it. Some hacks don't even support exFAT such as Lakka. There is absolutely no reason to use exFAT on the Switch; it is objectively inferior to FAT32. Also your CFW and homebrew will also be on the SD card as well as any cheats, mods, or whatever else you download so those will be lost if and when it corrupts if you use exFAT.
As for emuMMC, it can act as a cushion in the event of a brick since you can just remake emuMMC if it gets bricked. If your actual console is bricked, you either need a backup or shell out money for a new unit. It can also let you be on a higher firmware version without updating the actual firmware of your console. These are just a few advantages to using emuMMC.
Did you download your patches from this
thread? If not, I highly recommend you do so as that thread always has the latest working patches.
Did you follow a specific guide to migrate from SX OS to Atmosphere?