For further information on this change. The reason being is because they now use magical contagions instead of diseases. Monsters that previously inflicted a disease now just inflict the poison condition. Mundane diseases are not really mentioned in the rules. So spells or features that cure...
To try and clarify, I don't think you need to ask permission as the DM for a social skill against the PC in this context. It would just be a reverse of roles for the player and DM. The DM describes the NPCs social action and then the player decides if their character is influenced, not...
A bag of holding in 5e has a limit of 500lbs and a 64 cubic feet space limit. So unless your party is very light/small with minimal gear, you probably are only going to fit 2 people at most in an empty bag of holding. For example, My average sized valor bard human weighs about 240lbs between him...