Installing dlc and updates offline is extremely easy. Just find vid tutorials on installing .nsp files. If u are using sx os ts really just pasting a few files to correct spots on you micro sd card and pressing a few buttons on your switch. Its seems harder if you are trying download the nsp files directly from nintendo servers but they re all over the internet for u already. Just google dude.
I know u can download and install updates still after being banned. I d say never go online again with hacked switch. If online is important at all to you eventually get a 2nd switch, unless scene figures how to safely do it.