If it is true that the tongue is the antagonist of the masseter does that mean that the more force you push up with the tongue the more masseter activation you get?
Yes, assuming you keep the teeth in light contact. If the resting muscle tone of your tongue surpasses the masseters, you might find the mandible dropping, especially during sleep. If the resting muscle tone of you masseters surpasses your tongue, you might experience clenching or bruxism during sleep.