The ironic thing about this situation is that Twitter exercising their own judgement on what can and cannot be hosted on their platform is actually a good thing for the demonstration of independence of social platforms from government control.
Trump's departure from office plus the riot was where the balance was tipped (ie Twitter's potential future income from Trump's controversies was no longer greater than the reputational cost in keeping him on the platform).
I think not. I just don't think we'll ever have functioning legal frameworks for that.
Basically: freedom of speech and expression will only apply to what you do with your mouth, in the street. "Speech at scale", such as social media, will simply not be able to be included in it.
That might seem like a pessimistic take, but I don't think it is. The alternative is democratically elected governments taking a greater role in social media, effectively claiming services to be part of the substrate of society (Twitter, Streets...). I don't like that idea either. The lesser evil seems like the first scenario: freedom of speech not including at scale.