What is the form of celibacy fasting that would be a relief for those unable to marry, and are Monday and Thursday fasts sufficient to curb the soul's impulses, or should the Ayyam al-Tashreeq be added?

The Prophet, may Allah's prayers and peace be upon him, encouraged young people to fast when they are unable to marry, and he did not specify particular days for this. The best voluntary fasts are those that the Prophet سنَّ (instituted), such as fasting on Mondays and Thursdays, three days of every month, six days of Shawwal, the day of Ashura, and the day of Arafah, fasting the entire month of Muharram, and most of Sha'ban. For those who wish to fast more, the best form of fasting is to fast one day and break the fast the next, which is the fast of Dawud (David), peace be upon him. The young man should fast what achieves the breaking of his desires without weakening his body to the extent that he becomes unable to perform his duties.