Sacrifice X Lands. (X is 26, so I have to sac my 14 lands)
For each land sacrificed this way draw a card. (draw 14 cards for each land that been saced)
You may play X additional lands this turn. (X is 26 so I can play 26 more lands)
Lands you control enter the battlefield tapped this turn. (Amulet said no to this)
So if I'm correct, this card 1st ability is similar to Abolisher of Bloodlines that you have to sac as many creatures if lower then 3, that you have to sac 26 lands but you only can sac 14, so you have to sac as many as you can if lower then X, but still can play 26 additional lands
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Yes, everything checks out. Sacrificing the lands is not stated to be an additional cost, and Lithoforming doesn't target the lands, so you having less than 26 lands to sacrifice is not an issue, you just sacrifice all 14 you have. X is still 26, so you can play up to 26 lands this turn (in addition to your regular land drop for the turn).
Note, that each land you play after the Lithoforming does enter the battlefield tapped, triggering the Amulet, and when that trigger resolves you get to untap that land. And only then can you play the next land.