This is what i'll do.

1) Yes. For 10 coupon you can get 88 iron, X copper and blue - purple orbs. This is what i've seen. You are able to see what is in your 2nd "pull" so you'll be able to decide if it's worth to waste coupons on that.

2) I will buy a BP untill i get 4 tools, A or S. After that, i'll switch them for S as i get them, f2p style.

3) Dunno.

4) I burned 4k ingots, got 2 purple scrolls. So it's worth if you get something good to start. As we will get these scrolls from events like in CN (or so i hope), i don't see a reason to drop more ingots there.