Is the suitor entitled to retrieve what he offered in terms of a dowry and expenses after the fiancée's mother refused to complete the marriage?

Yes, you have the right to reclaim all the money and other things you paid, because the marriage did not take place, and the payment was made for its sake. The girl's family has no right to prevent her from marrying except for a legitimate religious reason, and they must return the money paid to you if the prevention was based on a legitimate religious justification.