Hi there anon! I'm sorry to hear what you are going through. Sorry to ask, but, within your archive, is there any private commissions? drawings done by yourself? pictures that are long gone from the internet or been purged from existence? If so, those pictures should be priority (do not use Mega to store them)
Also, have you checked for any duplicates? maybe you can shrink in size those 3tb automatically deleting duplicates using freeware.
And finally, 3tb is a fuck ton of information, using cloud storage would cost a lot... and uploading those files manually would take too much time.
As the board owner suggested, maybe torrenting is the best option, however it is not the best way to propagate your files or make them "survive" or be there for posterity, and given the size of it all, might also cause many people not wanting to download such a huge archive.
Given that your time is limited, trying to organize the files would be to much of a task, however if you can somehow, organize your files by "series" you have much more of a chance posting them on sites like
https://e-hentai.org/