First of all, during the consecration, he shouldn’t break anything. The fractioning of the host should occur at the Fraction Rite, which occurs while the schola and/or congregation is singing the Agnus Dei.
The General Instruction of the Roman Missal says the priest “takes the bread, and, raising it a little above the altar, says: “He took the bread, gave it to his disciples and said: Take this, all of you and eat it: THIS IS MY BODY which will be given up for you.” He shows the consecrated host to the people, places it on the paten, and genuflects in adoration.”
Now it is clearly implied that he should take a single host in his hand and explicitly says that he should show the host to the congregation.
Question 1: Is this valid? Yes. The words of the consecration must be altered (no pun intended) in order for the consecration to become invalid.
Question 2: Is this licit? Calling it illicit would probably be a bit harsh. The priest, if he isn’t showing the host at the time that he should be, is clearly not following the rubrics as he should, but I don’t know if calling it illicit is fair.
My bigger worry is that you seem to be used to the priest breaking the host at the consecration, which is blurring the symbolism of breaking the host during the Fraction Rite.
Adam