Is it permissible to say "faṭir" (فاطر) to refer to breaking the fast, or should one say "muftir" (مفطر) or "muftirah" (مفطرة), given that "faṭir" (فاطر) means "the Creator" and is mentioned in the Holy Quran (Fāṭir of the heavens and the earth)?

The correct statement for someone who informs about themselves that they are not fasting is to say: "I am muftir" (مفطر); because it is an active participle of "aftara" (أفطر - to break fast), and its noun is "al-fitr" (الفِطر) which is the opposite of fasting. As for "fatir" (فاطر), it is an active participle of "fatara" (فَطَرَ - to originate or create), meaning to begin and invent. It is permissible to use it for other than Allah Almighty, but it is better to say "muftir" (مفطر).