Plot questions - SPOILERS!!!!

Why did Michael want Gabriel to impregnate Valerie?

Just watched this movie yesterday and my head is still spinning. Danyael tells Valerie it was Michael's idea for him to impregnate her, but I don't remember anybody ever saying why Michael wanted that done. And Gabriel was spot on when saying when this type of thing happened before the results were terrible - giants roaming the land causing havoc (which is documented in Genesis and in Samuel). So it seemed Gabriel was trying to do the right thing by trying to prevent the birth of nephilim, but the movie made him out to be the villain.

And don't get me started with:

1. these archangels like Gabriel having to fist-fight like they were mere humans
2. Danyael impregnating Valerie with a nephilim and making her the target of Gabriel without her consent and then Michael saying at the end they can't protect her from Gabriel. What??? You put her in that position and then leave her to defend herself against an archangel??
3. the "good" angels only have a gate to keep the enemy out?? a superhuman enemy? For Pete's sake, a normal Joe could have climbed over that gate
4. Gabriel keeping Izzy alive to be his chauffer and Gabriel relying on technology like a computer, walkie-talkie and guns to complete his mission

Trying is the first step towards failure