Is it permissible for a Muslim man to marry a non-Muslim woman who believes in God but cannot change her religion due to family circumstances, provided she pledges to raise their children as Muslims?

You can conceal your Islam from your family by uttering the two Shahadas and practicing the rituals secretly. Prayer and fasting are possible without declaration. Your motivation for embracing Islam should be to please Allah Almighty and attain Paradise, not to marry a Muslim man. Obedience to Allah and His Messenger takes precedence over obedience to parents. Islam commands dutifulness to parents even if they are disbelievers, and your embracing Islam might be a cause for your mother's guidance.