Will a person be held accountable for his intention to fast a supererogatory fast if he abandons it due to work circumstances that prevent him from doing so, and he is unable to prepare food for iftar, and he does not want to burden his mother with the trouble of preparing food or worry her about him?

If your abstention from a voluntary fast is due to your compassion for your mother, then you are like those who intended to do a good deed but did not perform it, and one good deed will be recorded for you, as stated in the Hadith Qudsi. However, if the reason for abstaining is work from after 'Asr until midnight, then this ruling does not apply to you.