Is it permissible for a husband to refrain from spending on his pregnant wife and the expenses of the pregnancy, and to link that to her apologizing to his family, even though she believes she has not wronged them?

The spouses must live together amicably and the husband must provide for his wife. It is not permissible for the husband to withhold financial support unless the wife is disobedient by denying him his right or leaving the home without his permission. What you mentioned does not constitute an offense that warrants an apology or makes you disobedient.

Your husband must fear Allah, return to his home, provide for you, and live with you amicably, and clarify the matter to his parents.

If he insists on his stance, you have the right to take the matter to court to compel him to provide support. If you wish to appease him and apologize to his parents, it will elevate your dignity.