If the nonland card doesn't have a mana cost, its mana value is 0.

Demonlord Belzenlok's ability causes it to deal an amount of damage to you all at once; it doesn't deal 1 damage multiple times.

The mana value of a split card, such as a card with aftermath from the Amonkhet block, is equal to the combined mana cost of its two halves.

Land cards exiled this way remain exiled.

Once the triggered ability resolves, the ability will continue until you either exile a nonland card with mana value 3 or less or fail to exile any nonland cards while performing the process. You can't choose to stop receiving the blessings of Demonlord Belzenlok any sooner.

If the mana cost of the nonland card includes , X is considered to be 0.