2. It was a cross in the box to an open player. If the defender's arm is behind his back (a stance good defenders often take) he doesn't make the block. And the defender had the ability to get his arm out of the way. Instead he chose to use it to block the ball. I'd call that every time.

3. You sure? I've looked at that several times and it's not clear at all that's what it shows. The offside rule was made to be enforced in real time with the human eye. The combination of VAR and the offside rule (and the related inspection of grainy freeze frame images for a centimeter of toe or whatever) is frankly absurd.