But Obito's Izanagi didn't erase Minato's tag... It's stupid, I know.
Izanagi undoes what is disadvantageous to the user. What is disadvantageous to the user is decided by the user and Obito was fighting Konan and had no knowledge about the FTG mark as it wasn't relevant for 16 years so it wasn't undone for obvious reasons.
OT: Tobirama takes this mid difficulty. He can effortlessly dodge Danzo's fuuton or surprise attacks with Hirashin, top tier reflexes and sensory abilities. If Baku is summoned, it will be sometime later in the match much like it was against Sasuke in which case Tobirama by that time, should have set up markings all around the battlefield via shadow clones, allowing him to FTG behind Baku, away from its suction. A katon managed to oneshot Baku, a powerful slicing attack should cause it to be unsummoned.
As for stamina, Danzo had the edge against Sasuke due to Hashirama's cells but Izanagi proved to be chakra taxing for him despite against a character who couldn't spam his MS jutsus at the time. Tobirama has much more chakra than MS Sasuke so he isn't going to be tired during the fight. Danzo could try conserving Izanagi but that means he'll need to weave seals to use Izanagi again which isn't something Danzo can afford to do against Tobirama considering slower opponents compared to Tobirama have prevented faster opponents compared to Danzo to form hand seals.