Is it permissible for the husband to use all possible means to take his children to his country, in the event that his non-Muslim wife refuses to travel with him from Ukraine, fearing for them from moral decay?

When a husband and wife separate, the adult daughter stays with her father. As for the young children, the father has a greater right to their custody when the parents differ on the country of residence, and the children's best interest takes precedence. You must strive to bring your children to you and return with them to your country by all lawful means if their presence with their mother threatens their religion and morals. If your wife did not stipulate residence in her country before marriage, then it is obligatory for her to obey you in moving with you wherever you desire.