Adhesive hooks hold about 7.5 lb. A two-gallon pet fountain is heavier than that before you add the housing. The arithmetic no mounting guide does.
Mid-term, generally not. At renewal, generally yes. The exposure is not who owns the building, it is the date your term ends, and what to do first.
A silent lease generally is not a prohibition, and courts in most states read it that way. It is still not permission, and here is why to ask anyway.
Only the deposit is ever in play. Landlords must itemize deductions, and in some states missing the return deadline forfeits deductions entirely.
Under a joint and several liability clause, a landlord can pursue you for the full cost of your roommate's pet damage. What to write down first.