If a worshipper wishes to interrupt his prayer, should he say the tasleem twice, or what should he do? And should he say the tasleem if his ablution is invalidated, or is the prayer nullified, rendering the tasleem unnecessary?

It is not permissible to interrupt a fard (obligatory) prayer after commencing it without a legitimate Shari (legal) justification, according to the unanimous agreement of jurists. This is because it is an act of futility that contradicts the sanctity of worship, and there is a prohibition against corrupting an act of worship. However, interrupting it with a legitimate Shari justification is permissible, such as killing a snake, fearing the loss of valuable property, aiding someone in distress, or alerting a sleeping or heedless person whom a snake or similar danger is approaching. If the prayer is interrupted due to an event that nullifies wudu (ritual ablution), the worshipper does not need to do anything to exit from it.