I don't think hitting back would be WW3, I think he's just pushing at the edges to see what he can get away with. If we push back I don't think it is necessarily WW3 unless we go boots on the ground in Russia. If we hit the convoy, put peacekeepers in and enforce a no-fly zone I think we'll get a hell of a lot of sabre rattling, but I think it will ultimately be hollow.
He's lost decent numbers against Ukraine alone, without NATO in there too. His lines are struggling for fuel, food and morale before he loses his biggest convoy. He doesn't seem to have a decent counter for drone strikes, never mind modern fighters. Now seems like the time to push back before he reinforces that convoy and they start rolling again. If he gets control then it really is over for Ukraine and he has a future platform.