Touch of Death requires a melee hit

You do not spend the Channel Divinity before knowing whether the melee attack hits. The feature is triggered by a successful melee attack.

The damage scales with Cleric level

The extra necrotic damage is 5 + twice Cleric level, so it remains relevant as the character advances.

Inescapable Destruction covers Channel Divinity

Because Touch of Death is a Channel Divinity effect, its necrotic damage benefits from Inescapable Destruction at 6th level.

Resistance is ignored, immunity is not

The feature says your relevant necrotic damage ignores resistance. A creature that is immune to necrotic damage remains immune unless another rule explicitly changes that immunity.

Cleric spells also benefit

Necrotic damage from your Cleric spells likewise ignores necrotic resistance, improving the reliability of the Domain's necromancy-focused spell package.

Divine Strike is a separate feature

The 8th-level Divine Strike deals necrotic damage from a subclass weapon feature, not from a Cleric spell or Channel Divinity. Do not automatically apply Inescapable Destruction to every necrotic source without checking the exact wording.