I've heard that it's not good to name after someone who has suffered bad mazel, but are there any halachic prohibitions against it? It apparently means "persecuted" but Miriam means "bitter" so they don't all need to have pleasant meanings, right? I really appreciate the message of remaining faithful even when it isn't easy. Just wondering!
It's not entirely clear to me what you mean by 'halachic prohibition', but if you mean do halachic authorities rule that you shouldn't name after people who underwent certain negative experiences, the answer is yes. See here for example. The reason behind it is that it could potentially harm the child, which would seem to be a more important consideration than any positive message expressed by the name. That being said, however, whether Iyov technically falls into that category is a separate question. Additionally, even if he does qualify as 'רוע מזליה', there may be ways around it, such as adding an additional name. A Rabbi should be consulted.