Under 30 million I suspect (surveys meaningless). Since I have read WWII history, if I was living in Russia, I'd support the war too. Why be one of the ones executed a few days before Putin ends up dead?
What if Zelensky had fled to Europe? It's sort of a miracle things have turned out as they have, so far. If they didn't, Putin would be the hero of the U.S. right. 50 million Americans would talk a Trump/Putin ticket in the 2024 election--never mind Putin is Russian.
I watch many interviews of Russians on YouTube. I get the sense most know what's going on. Many of their answers are funny in that Russian fatalistic way. Think about being 80 and looking at ending your life as part of country that kills children? She just can't go where you can go, your life ahead of you. I believe I understand what your Mother in Law is dealing with. Paralized fear. You say yourself she doesn't study the news. I hope you and your wife can talk to her more.
One of my favorite movie line, "A man is only big as the things that make him mad" What any old Russian person thinks about the war doesn't matter.