Is it permissible to proceed with marriage to someone who has started to change the agreements made during the engagement, after having previously shown high levels of religiosity and good character?

If the suitor is a man of good character and religious commitment, then the matter should be made easy for him, and he should not be burdened with what he cannot bear, as that could be a reason for him to withdraw.

If he desires to get married and requests a change in financial matters that burden him, we advise easing them for him and agreeing to his request; for the Prophet, peace and blessings be upon him, said: "The most blessed of women are those who are the least burdensome in expense," and in another narration: "The most blessed of marriages are those that are the least burdensome in expense."

The guardian should be persuaded to reduce the dowry. If you cannot speak to him directly, then have someone else speak with him.

However, if the suitor has changed his mind and is requesting a change in conditions as an excuse to reject the engagement, then breaking off the engagement before the marriage contract is better for the sake of avoiding negative consequences.