He cast “Gentle Repose”, and that was just to get Utrix’s weird corpse bugs off of him, not to make his body last longer. The spell does protect the body from decay, but Ramus technically(?) isn’t dead. Adam specifically mentioned when he cast it that nobody had ever thought to try to cast it before on a living person, which is why the fact that it did anything to Ramus (his soul started reacting in heaven, temporarily drawing the attention of a Celestial) has probably more to do with his spiritual state than his physical one.
He doesn’t have an upper soul, but he does still have the lower one, and he still needs air, food, and water, and can still naturally heal, meaning he is (probably?) still physically alive.
Although, what exactly “being alive” means in CoS has a lot to do with having a soul, and Adam may have been meaning nobody had thought to cast it on a living corpse, but I think you can see my point.