1. Here's a radical thought. Why don't we pay to have a man running along the touchline watching at full speed? He could maybe have a flag that he raises if he thinks it's offside, while giving the benefit of the doubt to the striker.
2. It'll still be subjective. Fans will think they've been robbed.
3. Ditto. If the penalty had not been awarded, Wolves fans would have been baying for blood as, in their opinion it was quite clearly a handball.
I'm also too much of a student of human nature to expect referees to overturn their own decisions. There are too many cognitive biases that lead you to support decisions you've already made. It's even worse if you've announced a decision (that's why they tell you to inform others that you've given up smoking - it's tougher to go back on something you've made public). Add in the fact that a changed decision makes it look like you can't judge in real time and I wouldn't hold out hope for many revocations of decisions.
If you really want better decisions, there's a wealth of evidence to show that referees wearing headphones playing white noise make far better decisions than referees who can hear the crowd. That's a technology I'd support.
Vin