Is it permissible for a woman to remove her head covering (khimar) and suffice with a loose abaya while concealing her facial features as much as possible, along with committing not to go out except out of necessity and not to mix with non-mahram men, if wearing the khimar would expose her and her husband to harm, for the sake of stability and protection from tribulations?

We understand that the questioner, by khimar, means a face covering, not a head covering, because she is trying to conceal some of her facial features. If this is what she intends, then despite the scholarly disagreement regarding the obligation of covering the face—with our preferred view being that it is obligatory—if a woman who wears the niqab fears significant harm, there is no harm in her uncovering it to avert such harm, taking the view of those who do not consider covering it obligatory. This is provided that the rest of her body is covered according to the conditions of the shar'i hijab (definition).