Hey, I'll try to give my input. If you are trying to find a replacement for Impulse, how about Preordain? And for Latnam's Legacy, I echo Conboy31 highly recommend Show and Tell because it puts it into play and that is your goal after all.
I personally don't like Blessing, Hurkyl's Recall, or any other card that can be dead if you draw it. You already have enough dead draws in the form of creatures/keyvault anyway, don't need to add more in my humble opinion.

If it works for you though, keep on going.
Good luck with your build, if you discover anything that you think is a breakthrough please do share!