What is the most standardized way to handle spells from a template?

I need help with a specific piece of a problem in a game I’m running, which generalizes to the question title.

Specifically, there is a big bad dracolich somewhere that the players want to be. They have a cunning plan to simply wish the dracolich away to a different place. They have access to wish through an essentially homebrewed acquired template that one of them has gained (a spiffier version of Smoking Eye Creature, from the Shackled City campaign path). The template is tied to a demiplane, and the wish effect works once/year, and the demi-plane eats the xp cost.

I have existing houserules that say wish can essentially only be used for the explicitly listed uses (it does those things without issue, and is actively malicious about perverting or failing any off-label wishes). However, this is one of the listed effects:

A wish can lift one creature per caster level from anywhere on any plane and place those creatures anywhere else on any plane regardless of local conditions. An unwilling target gets a Will save to negate the effect, and spell resistance (if any) applies.

This is where it breaks down: I haven’t specified a caster level or save value for the wish ability. What would be the most standardized way to determine those?

I’m really looking for a textual basis for this. I know there are not exact rules to cover this situation (are there?), so a good answer will probably explain how this matches some existing pattern, and have a clear method for finding caster level (for SR) and saving throw DC.