Is my not speaking to my mother, due to her harming me, considered disobedience to parents (ʿuqūq)? And will my prayer for a righteous spouse be answered despite people not knowing me, and despite the devil's whispers that I should first take practical steps?

The mother holds a great status in Islamic law, and three-quarters of piety are due to her. What you mentioned about your mother's injustice is general, and the اصل (fundamental principle) regarding a mother is compassion towards her children, so you should think well of her. It is not permissible for you to abandon your mother and stop speaking to her, as this is an act of disobedience (العقوق). Even if you dislike her actions in your heart, you must beware of any behavior that harms her. You should offer her advice and clarify her mistakes, seeking assistance from some virtuous individuals, and make abundant supplications (دعاء). You must repent from sins so that the supplication is not hindered from being answered.