Would any hard sticking glue / glue gun work to help hold something 5-10 pounds onto drywall?
You can put the best adhesive in the world on there but if there is nothing to glue to, drywall, it won’t be worth a flip. I would go to the hardware store and invest in some of those fancy drywall hanging devices they have now days, they make a bunch that are really strong, grab the drywall and hold good. Your basic butterfly would work good. Hot glue is good for temp cardboard only. I haven’t found it very good on anything. Polyurethane is excellent exterior caulk, but very expensive, stays flexible and sticks to water, but won’t hold tight. So no matter what size hole you have, they have a drywall hanger for you and the cost is minimal.
