The display has only one visual setting.
The weir gate floats free and should stay at the water level. When the pump is on, it will drop down and water should cascade over it. When the pump turns off, the weir gate should automatically rise to prevent any leaves, or other debris, to backflow into the spa.
The heater leak, first take some paper towel and dry up where you see it leaking and with a bright light observe "where" the water first appears. Two options, the front of the heater that you can see, and the back of what you can not see. If you see the water, as it first appears, coming from the seam, this is serviceable.
However, the first question would be how long has it been leaking. It is uncommon for the heater to leak, unless you have had a freeze occurrence. IF the leak can not be seen on the front, it could be coming from a freeze crack on the backside.
Either way, remove the heater removing the 2 nuts and washers; disconnect the black and red wires, and carefully removing the hi-limit sensor in the dry well at the top of the heater during the removal process. This can be done with water in the spa IF you "clamp" the hose coming from the circ pump, and the hose coming out of the top of the heater with vice-grips. Observe inside the heater to see 8 to 10 screws holding the parts together. There is a thin metal plate with a stem attached to it that will pullout.
There is an o-ring that could be leaking (not likely), but if it is coming from the seam of the 2 parts, apply a bead of silicone around the perimeter and reinstall, allowing time to cure prior to putting water under pressure once again.
If this fails, you may have a "hairline" crack that IF found could be epoxied as Tman suggested if it can be discovered, a bright light helps, otherwise the heater needs to be replaced.
