I don't know. That's something you'd probably have to ask them, but I think you might be able to get away with it if you're experienced enough. Worth trying, anyway.
Anything is an enemy that could be brought here. That's the downside of the tesseract. But the upside of being "fictional" in this world means everything's online and easily linked. This will give you a fairly good idea about what they're like. You can skip over the "History" and "Story" sections, unless you're really curious.
I'm sorry about your parents. And about Eren's mother. But I'm glad you have a friend like that. Those people are important.
Those sound... unpleasant. Is there a particular way to fight against them?