you can, but to be more efficient i recommend that you don't just so your not really wasting water but what you can do is get a pool cover so nothing gets in the water.
You need to replace the water that evaporates.
If its too high you have to dump water and replace it with fresh water be carefull to work out how much water you need to replace you wouldn't want to have to do it again. If the pool drain goes into the public sewers ensure there are no local rules affecting such discharge, or that you have the necessary consent.
Yes. The water will evaporate, leaving the salt behind. Let the process go on long enough, and you'll have a brine pool of VERY salty water. The only way that salt gets out of the pool is when swimmers track the salt water away as they walk away.
drain some of the water out of the pool and replace with fresh water it would probably pay to work out how much to salty so you can work out how much water to drain.
Dilution. You would need to drain and replace some of the water in the pool.
I would replace it every few days, for a normal small pool in back yard. If you have a large in ground pool, you need not change it but every few weeks. As long as you use the proper chemicals.
If your pool is above ground it does not matter, But if your pool is in ground and you drain it it will act like a boat and float if the water table rises.
You need to dilute or change the water only when one or both of those levels exceed desired levels. There is no regular schedule for this, as the levels and their increase rate will vary from pool to pool. Get reliable test equipment and test the water yourself periodically, or take a fresh sample of water in to your local pool store to have the levels checked.
Yes, many pool supply companies sell candles holders that float in water. You can keep the holder for years and replace the small candle inside.
Probably the least expensive is to replace some or all of the water(dependind on hardness) with fresh.
It sounds like there is a broken water line under the sand. Perhaps from a sprinker system?
Above ground pool pumps are made to sit at or below the water level, not to pull water up. If placed above the water level, or away from the pool-side they will not circulate the water properly and may not even prime. For your well, a better option is to go for an in-ground pool pump - or better still, purchase a pump made for your particular application.