Shocks and coolant loss

G'day Telha.
The shocks have a line running to them that allows for an adjustment to the valving, hence difference in ride.
If you take the vehicle off road, engage the harder setting, you will notice the difference. Less float and an obviously more firm ride. It's more comfortable off road.
You should be able to notice on the highway as well. (I can on mine, though I will soon replace it with an ARB Old Man Emu setup.)

Re coolant loss.
Have you replaced your thermostat with one more suited to your country? The original Japanese thermostat will have the wrong temperature setting.
I'd be looking around my head very closely. Do you have bubbles in your header tank? Get your mechanic to pressure test your cooling system, or find another mechanic.
Your coolant loss is exessive.I live in Tropical North Queensland (AUSTRALIA) and it's 32 deg Celsius most days and I drive 120 -150 km per day on the highway. Towing has been no problem and I have had no coolant loss what so ever.

Best wishes Telha.

Ken.