The "fan," ExoVerseVT, was a friend of hers which she has met in real life at least once. That's why she got embarrassed when he appeared in chat right while she was making some lewd comment.
The guy apparently has connections, but I don't recall anything that seemed to imply Lia wanted to get into voice acting.
The guy was most certainly not a prick and in fact started the call by complimenting her on her stream as well as complimenting the fans for their devotion, from what I recall. He did say he wanted to hang out with Lia IRL some more. I was unfamiliar with the guy but I came away with a pretty good impression of him.
Lots of ironic "M*LE VOICE ON STREAM" in chat, sure, but the viewership numbers seemed to remain steady from what I recall. Everyone seemed to have a good time. At some point he started reading lines from the Thresh foot fanfic and many in chat (including myself) were calling for him to continue for the lulz.
Apparently. I'm not sure what annoyed Tenma to make her do this. I don't recall seeing him saying much in chat after he left the call.
If what was posted here earlier was really from her roommate, yes, but it's not clear what she was sadposting about, and it needs to be remembered it was posted in the context of her being mentally exhausted and drunk on an empty stomach. I wouldn't read too much into it.
Stop reading /vt/. Here, make your own decisions. Here's the stream timestamped to when she notices Exo in chat:
And here it is when he joins the call: