1. As most of the other healers / immortals in the City have it as a part of them as well, we're inclined to say no. His healing ability would end up dropping down to that of a normal human being, though only for the duration of the plot. As soon as he leaves, it'll be back to normal.
2/3. It will be allowed, but with the caveat that it's slightly more draining than it usually would be. Additionally, use your judgement on just how strong and fast he ends up being, with the knowledge that powers may not be up to full capacity within the Coliseum.
4. It's the Coliseum itself that's doing the nerfing, in addition to the Magistrates' power.
5. There won't be any guns found within the Coliseum, but Dante will be allowed to have his guns with him, they just may not work as well, and he won't be able to find ammo for them. See also Boyd's above question for further details!
ALWAYS GOOD
2/3. It will be allowed, but with the caveat that it's slightly more draining than it usually would be. Additionally, use your judgement on just how strong and fast he ends up being, with the knowledge that powers may not be up to full capacity within the Coliseum.
4. It's the Coliseum itself that's doing the nerfing, in addition to the Magistrates' power.
5. There won't be any guns found within the Coliseum, but Dante will be allowed to have his guns with him, they just may not work as well, and he won't be able to find ammo for them. See also Boyd's above question for further details!