Running out of soft water and confused by softener settings
As suggested by Mattman944's comment, you may have a salt bridge. That's where the salt sticks together to form a crust near the top of the tank, but it's actually empty at the bottom, and therefore isn't creating the brine necessary to clean the resin tank. Poking at the top of the salt (be careful, you don't want to jab through the plastic of the tank and cause a crack and a leak) should break any salt bridges and allow you to properly fill the salt basin.

More importantly, how often is your softener set to cycle? If you have a manually set cycle, you may need to increase the frequency/reduce the days between cycles. If it's set to run every 5 days, reduce it to every 4 days to see if that fixes the problem. If you're still running out of soft water, reduce it to every 3 days. Lather, rinse, repeat until you're happy with your soft water supply.

If it cycles automatically when the water gets hard (ours does that - a lovely feature), it may be that the sensor mechanism is malfunctioning. Check your manual for troubleshooting tips and/or contact the manufacturer. If there is a failure, it may still be under warranty.