I always assume all NO 'miracles' are from the devil as the new rites are doubtful and therefore must be treated as invalid. I can see no logical reason for them other than keeping people in the NO religion and making them think the new rites are ok.
Of course. I've said this from the beginning. Please explain what would prevent the devil from simulating a Eucharistic miracle. If God permitted it, the devil could simply obtain some human flesh and swap a little piece of the bread out for it. At one point, in the case of the one nun during the Middle Ages who had everyone fooled, the devil even simulated a "virgin birth".
That's why the Church has NEVER based theology in "miracles" or "private revelations", but the other way around. If something fails a theological standard, it's rejected by the Church immediately without any further investigation required.
Let's say the New Mass is invalid. Wouldn't the devil do whatever he could to make people think it was valid? Absolutely he would.