A fast review on the quoted ahadith
The hadith of 'Abdullah ibn 'Awfa has been qualified as da'if even if it differs slightly of other sahih ahdith like your second quoted hadith which you may find in sahih Muslim, sunan abi Dawod, Jami' at-Tirmdihi and in both the sahih and al-adab al-mufrad of al-Bukahri.
The last hadith is originally from sahih Muslim: What one could deduce from it is that if you could do your best to keep the ties of kinship and you could be patient while your relatives are treating you badly you may be rewarded in the hereafter. So this is an other way to emphasize the importance to maintain ties of kinship. See also this fatwa with more details on the importance of maintaining ties kinship.
Gracious avoidance الهجر الجميل
Allah the Almighty said addressing his Messenger (Peace be upon him):
And be patient over what they say and avoid them with gracious avoidance. (73:10)
so beside patience a way to treat relatives whom we may fear or fear their abuse ... there's the so called gracious avoidance.
According to this Fatwa (in Arabic) quoting at-Tahar Benachour gracious avoidance means: that one is asked to do avoidance literally that means not meeting somebody, to have no social relation with him/her but without any bane or any kind of vengeance or dislike. This means you shouldn't talk badly or abusing or any bad words or acts.
Ibn Taymiyah said (My own translation take it with care or feel free to suggest editing):
الهجر الجميل هجر بلا أذى، والصفح الجميل صفح بلا عتاب، والصبر الجميل صبر بلا شكوى
The gracious avoidance: is an avoidance without bane, the gracious forgiveness: is a forgiveness without blame and gracious patience: is a patience without beef
Ibn 'Abd al-Barr explained that gracious avoidance is allowed if one fears due to social relation a harm in his faith or his Dunya (this life) and an increase of animosity and hatred. So avoiding in those cases is safer then to approach and maintain ties. As it would prevent you from slips as you will be safe from aftereffects of this company.
On maintaining ties of kinship to non-Muslims
According this Fatwa (in Arabic) a Muslim isn't asked to maintain to maintain the ties of kinship to a non-Muslim (literally a kafir) relative (in means of affection) even if it was a brother, sister etc quoting the story of Noah and his son in (11:46) which may indicate that a disbeliever is no more considered as a relative to a Muslim and (58:22) which adds even the parents and kids if they were disbelievers and oppose Allah and Islam.
But it is allowing to keep the ties for allowed wordily matters like making gifts especially if there's a hope that this person could convert or at least be positive about Islam based on verse (60:8) and in case of the parents (31:15). See also this sahih hadith and this about giving gifts see also this hadith on a statement about the paternal relatives of our Messenger (Peace be upon him) see also in sahih Muslim. According to ibn Hajar in fath al-Bary ibn Battal concluded that this last hadith indicates that the wilaya الولاية translated protection or guardianship or friendship (the two first are closer to the Arabic meaning) is ordered for the faith and banished for the kinship.
More references and conclusion
For further information here is a fatwa in English On how to deal with a relative who is an apostate.
Note that on islamqa I found a fatwa allowing the gracious avoidance as described above even for Muslims see for example here for relatives who abuse and threat others badly and one where a mother (Muslim) is allowed to avoid her (Muslim) if she is abusing her, but this fatwa is also recommending patience and quoting ahadith on the importance of maintaining ties of kinship.
So in your situation you are the best to know what is more convenient: you can show patience and keep at least a minimum of the ties of kinship in the hope of being rewarded by Allah or avoid a gracious avoidance.
Note you could keep the ties by a simple phone call asking how things are, no more no less or being as much neutral as you can!
And Allah knows best!
