Is it obligatory to make up for the days following the day of breaking the intention in Ramadan, given that their number or dates are unknown, and there is no certainty about renewing the intention therein, and does this entail offering expiation?

If it is merely hesitation in breaking the intention of fasting, then the fast is not invalidated. However, if the intention to break the fast is firm, then the fast is invalidated. It is sufficient to make up one day for the day whose fast was invalidated.

The intention for fasting does not require verbalization; rather, its place is the heart. So, whoever eats suhoor for fasting has intended, and whoever thinks in his mind that he will fast tomorrow has intended. It appears that you were making the sufficient intention, and you do not need to make up the fast.

Sheikh Ibn 'Uthaymeen says that if a person wakes up late at night and eats suhoor, he is intending to fast, for there is no voluntary action without an intention.

Sheikh al-Islam Ibn Taymiyyah says: "Whoever thinks in his heart that he will fast tomorrow, has intended."

Beware of waswas (whispers/obsessive thoughts) in this matter.