Well, the point is, that you try to follow different strategies, and some of them work better with your main plan (life gain/loss) than others.
Let's have a look at some cards:
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God-Pharaoh's Statue: fine by itself, but with your current mana base, I doubt you'll be able to play it before turn 8 and I'm not sure it's still important at this point of the game. I would prefere it in a artifact deck, where you'll be able to play it at turn 3-4.
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Voltaic Key: a great piece for alot of combos, but in your deck? you got 6 possible targets, 3 of them would give you a little extra mana and the other 3 might be usable a second time.
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Mindcrank: great for alot of mill strategies. but in your current deck it feels a little lost, since there little synergy besides some life loss.
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Keening Stone: this may result in alot of milled cards. but its expensive to play and use, AND you'll need a significant amount of cards in your opponents graveyard, before it's making sense to activate it.
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Night Dealings: a interesting card for tutoring on a budget. but there is a little problem: life loss != damage.
I could point out some more cards here, but I think you'll understand what I'm trying to say. I would suggest you to focus a little more on the lifegain/loss.
Some cards that are comming into my mind that could fit a little more:
Soul Warden,
Soul's Attendant,
Authority of the Consuls,
Aetherflux Reservoir,
Ashnod's Altar,
Luminarch Ascension,
Campaign of Vengeance,
Phyrexian Processor.