Lorem ipsum, I am curious on whether this will go through to Mastodon regardless of the character limit, because I think I have seen over 500 characters over there. I also hope tagging NSFW i

At least next time I will know to type long stories at Hubzilla and then boost them at Mastodon if I have trouble staying under 500 characters.
Since mastodon abuses summary for content warnings, you would need to use the summary tag to get a content warning in mastodon:

[summary]your content warning[/summary]

For the lost n.s.f.w tag: you used the hubzilla categories for this. Masto does not have categories iirc so we can't map them to anything useful...
Thanks, I will keep that in mind for the next time :)