The nail on the head replace the head replace the head replace the nail on the head replace the nail on the nail on the head.
The sand its cumbersome but very cheap.
The air leak is the reason you can’t get enough suction to vacuum the pool. You may be able to vacuum if you can isolate your skimmer and drain lines. (that will depend on how the pluming was configured when the pool was built) If the air leak is in the skimmer line adjust your valves to only pull from the main drain. If you can’t adjust the valves from skimmer and drain, Tell the pool service company the will need to porta vac the pool. They don’t all have the equipment and if they do they don’t always have it with them. As far as the sand in the filter is concerned it won’t prevent you from vacuuming. It should be changed about every 5 years. One of the symptoms of old sand are, pool won’t clear (cloudy). That doesn’t sound like your problem.