Is it permissible to transfer my father's body after he was temporarily buried in an Islamic cemetery in the Netherlands to Syria, in accordance with his will, and is he considered a martyr given his health condition and operations?

If you are able to bury your father where he wished, then there is no harm in it. However, if you bury him in the Muslim cemeteries of that country, then it is not permissible for you to move him thereafter, because the aforementioned purpose is not among the necessities that permit moving the deceased. If he dies due to this disease, we hope that he will be among the martyrs of the Hereafter.