As fas aa I know, that is boot0 issue.You can get clean boot0 by using EmmcHaccGen to generate boot0, but you must have a working prods.key to extract boot0.
I guess that your switch can be fixed by way of donor nand method but you must have the prod.keys of your bricked switch, donor nand prod.keys and donor nand.
If boot0 is corrupted by Choi , you can get donor's boot0 from the video tutorial available on Utube.In that video tutorial, there are three boot0 files which covers for all models.
As fas as I know, you don't need to dump sx pro dongle in order to reflash it with atmosphere.There is a python script which converts third-party payloads to custom boot.dat to work with sx pro dongle directly.
I guess that your switch would be a patch version with lower firmware which can make an access to homebrew channel. If you performed system update on your switch with Choidujounx , it would turned on auto rcm which bricked your switch as your switch does not support auto rcm.