Concubinage and “what the right hands possess”: is there a concept of marriage-less union, and does the Qur'an endorse abuse?

وَإِنْ خِفْتُمْ أَلَّا تُقْسِطُوا۟ فِى ٱلْيَتَـٰمَىٰ فَٱنكِحُوا۟ مَا طَابَ لَكُم مِّنَ ٱلنِّسَآءِ مَثْنَىٰ وَثُلَـٰثَ وَرُبَـٰعَ ۖ فَإِنْ خِفْتُمْ أَلَّا تَعْدِلُوا۟ فَوَٰحِدَةً أَوْ مَا مَلَكَتْ أَيْمَـٰنُكُمْ ۚ ذَٰلِكَ أَدْنَىٰٓ أَلَّا تَعُولُوا۟

And if ye fear that ye will not deal fairly by the orphans, marry of the women, who seem good to you, two or three or four; and if ye fear that ye cannot do justice (to so many) then one (only) or (the captives) that your right hands possess. Thus it is more likely that ye will not do injustice.

۞ وَٱلْمُحْصَنَـٰتُ مِنَ ٱلنِّسَآءِ إِلَّا مَا مَلَكَتْ أَيْمَـٰنُكُمْ ۖ كِتَـٰبَ ٱللَّهِ عَلَيْكُمْ ۚ وَأُحِلَّ لَكُم مَّا وَرَآءَ ذَٰلِكُمْ أَن تَبْتَغُوا۟ بِأَمْوَٰلِكُم مُّحْصِنِينَ غَيْرَ مُسَـٰفِحِينَ ۚ فَمَا ٱسْتَمْتَعْتُم بِهِۦ مِنْهُنَّ فَـَٔاتُوهُنَّ أُجُورَهُنَّ فَرِيضَةً ۚ وَلَا جُنَاحَ عَلَيْكُمْ فِيمَا تَرَٰضَيْتُم بِهِۦ مِنۢ بَعْدِ ٱلْفَرِيضَةِ ۚ إِنَّ ٱللَّهَ كَانَ عَلِيمًا حَكِيمًا

And all married women (are forbidden unto you) save those (captives) whom your right hands possess. It is a decree of Allah for you. Lawful unto you are all beyond those mentioned, so that ye seek them with your wealth in honest wedlock, not debauchery. And those of whom ye seek content (by marrying them), give unto them their portions as a duty. And there is no sin for you in what ye do by mutual agreement after the duty (hath been done). Lo! Allah is ever Knower, Wise.

وَمَن لَّمْ يَسْتَطِعْ مِنكُمْ طَوْلًا أَن يَنكِحَ ٱلْمُحْصَنَـٰتِ ٱلْمُؤْمِنَـٰتِ فَمِن مَّا مَلَكَتْ أَيْمَـٰنُكُم مِّن فَتَيَـٰتِكُمُ ٱلْمُؤْمِنَـٰتِ ۚ وَٱللَّهُ أَعْلَمُ بِإِيمَـٰنِكُم ۚ بَعْضُكُم مِّنۢ بَعْضٍ ۚ فَٱنكِحُوهُنَّ بِإِذْنِ أَهْلِهِنَّ وَءَاتُوهُنَّ أُجُورَهُنَّ بِٱلْمَعْرُوفِ مُحْصَنَـٰتٍ غَيْرَ مُسَـٰفِحَـٰتٍ وَلَا مُتَّخِذَٰتِ أَخْدَانٍ ۚ فَإِذَآ أُحْصِنَّ فَإِنْ أَتَيْنَ بِفَـٰحِشَةٍ فَعَلَيْهِنَّ نِصْفُ مَا عَلَى ٱلْمُحْصَنَـٰتِ مِنَ ٱلْعَذَابِ ۚ ذَٰلِكَ لِمَنْ خَشِىَ ٱلْعَنَتَ مِنكُمْ ۚ وَأَن تَصْبِرُوا۟ خَيْرٌ لَّكُمْ ۗ وَٱللَّهُ غَفُورٌ رَّحِيمٌ

And whoso is not able to afford to marry free, believing women, let them marry from the believing maids whom your right hands possess. Allah knoweth best (concerning) your faith. Ye (proceed) one from another; so wed them by permission of their folk, and give unto them their portions in kindness, they being honest, not debauched nor of loose conduct. And if when they are honourably married they commit lewdness they shall incur the half of the punishment (prescribed) for free women (in that case). This is for him among you who feareth to commit sin. But to have patience would be better for you. Allah is Forgiving, Merciful.

وَٱلَّذِينَ هُمْ لِفُرُوجِهِمْ حَـٰفِظُونَ

And who guard their modesty -

إِلَّا عَلَىٰٓ أَزْوَٰجِهِمْ أَوْ مَا مَلَكَتْ أَيْمَـٰنُهُمْ فَإِنَّهُمْ غَيْرُ مَلُومِينَ

Save from their wives or the (slaves) that their right hands possess, for then they are not blameworthy,

وَأَنكِحُوا۟ ٱلْأَيَـٰمَىٰ مِنكُمْ وَٱلصَّـٰلِحِينَ مِنْ عِبَادِكُمْ وَإِمَآئِكُمْ ۚ إِن يَكُونُوا۟ فُقَرَآءَ يُغْنِهِمُ ٱللَّهُ مِن فَضْلِهِۦ ۗ وَٱللَّهُ وَٰسِعٌ عَلِيمٌ

And marry such of you as are solitary and the pious of your slaves and maid-servants. If they be poor, Allah will enrich them of His bounty. Allah is of ample means, Aware.

وَلْيَسْتَعْفِفِ ٱلَّذِينَ لَا يَجِدُونَ نِكَاحًا حَتَّىٰ يُغْنِيَهُمُ ٱللَّهُ مِن فَضْلِهِۦ ۗ وَٱلَّذِينَ يَبْتَغُونَ ٱلْكِتَـٰبَ مِمَّا مَلَكَتْ أَيْمَـٰنُكُمْ فَكَاتِبُوهُمْ إِنْ عَلِمْتُمْ فِيهِمْ خَيْرًا ۖ وَءَاتُوهُم مِّن مَّالِ ٱللَّهِ ٱلَّذِىٓ ءَاتَىٰكُمْ ۚ وَلَا تُكْرِهُوا۟ فَتَيَـٰتِكُمْ عَلَى ٱلْبِغَآءِ إِنْ أَرَدْنَ تَحَصُّنًا لِّتَبْتَغُوا۟ عَرَضَ ٱلْحَيَوٰةِ ٱلدُّنْيَا ۚ وَمَن يُكْرِههُّنَّ فَإِنَّ ٱللَّهَ مِنۢ بَعْدِ إِكْرَٰهِهِنَّ غَفُورٌ رَّحِيمٌ

And let those who cannot find a match keep chaste till Allah give them independence by His grace. And such of your slaves as seek a writing (of emancipation), write it for them if ye are aware of aught of good in them, and bestow upon them of the wealth of Allah which He hath bestowed upon you. Force not your slave-girls to whoredom that ye may seek enjoyment of the life of the world, if they would preserve their chastity. And if one force them, then (unto them), after their compulsion, lo! Allah will be Forgiving, Merciful.

إِلَّا عَلَىٰٓ أَزْوَٰجِهِمْ أَوْ مَا مَلَكَتْ أَيْمَـٰنُهُمْ فَإِنَّهُمْ غَيْرُ مَلُومِينَ

Save with their wives and those whom their right hands possess, for thus they are not blameworthy;