What are the implications of my statement "I covenant with Allah" that I will seek a Muslim wife if He saves me from distress and the fetus is aborted, especially given the difficulty of marrying a Muslim woman in Western countries?

The fatwa (definition) is that whoever says, "I covenant with Allah concerning such and such," and then breaks that covenant, an expiation for breaking an oath becomes incumbent upon him. If you intended to marry a righteous Muslim woman in your country and did not find her, then no breach has occurred and no expiation is incumbent. We should note that marrying a Muslim woman, even if she is deficient in her religious practice, is better than marrying a woman of the People of the Book. Furthermore, it is not permissible to abort a fetus at any stage of pregnancy.