1) Where should I mount it?
140 grams will certainly affect the flight, but assuming you get a balance-neutral placement it should still fly in good winds. That position can be at the center of mass on the kite, or it can be on the tow point. Kites can carry relatively heavy loads, including cameras. Assuming wind is strong enough the critical factor is not the weight, but how that weight is distributed to keep the kite balanced.
As long as it remains balanced, it shouldn't harm flight too badly.
2) Should I adjust the tow point?
You can move the tow point toward the nose if you want. It changes the pitch, the angle that the kite flies at. Closer to the nose usually makes it move forward more forcefully, up to a point. You can choose which point to use when you are out in the field.
2.2) Should I change it in higher winds at an altitude?
I'd choose based on trial and error. Try it with the lower setting first, point B. If there is not enough lift, try the upper setting, point A. If it is strong or uncontrollable, bring it back down and make adjustments.