Temperature rosed to 3/4 the temperature gauge.

The engine barely heats, i have low temperature on the gauge, and also from the cabin heater not much. Especially in the winter the temperature gauge of the engine barely moves, when i’m turning on the heating in the cabin, the arrow drops to zero. I’ve changed the thermostat, got rid of air pockets, coolant level is ok, changed the temperature sensor on the engine block. I’ve noticed few days ago that the rubber hose that is clamped to the thermostat is weeping a bit, i can see a slight residue of coolant crystallised. Could it be that it’s sucking air in the system? Besides that what could it be? Thank you!