If the intervener is overcalled by a responders to the 1NT what are the options for the advancer in addition to the standard responses. Is he now allowed to pass meaning partner I cannot help.
Your partnership agreement for Capelletti is as outlined on Wikipedia
Absolutely Advancer can pass; the work of interference has been performed. Doing so is a de facto statement by Advancer that he is uninterested in continuing the auction, either because of a paucity of points or lack of fit or both.
The general philosophy is the same for a preemptive opening at the 2-level or higher: the initial bid should be so descriptive that there is no temptation by the initial caller (Intervenor in this case) to continue the auction unilaterally.