Meenu made a ordinary happy go lucky man like Kunal filled with hate, dejection and rejection. He was willing to find love with Shweta, Mishti but is now suffering from the baggage of his mothers games and cannot go over even with normal day to day life. Actually poor Kunal did not hide the unhappiness in the marriage, and revealed it to all most importantly Mishti. Abhir did not reveal the most imp fact of Kunal running away.
Kuhu is layered, has shades of grey, not sure if she eill become grey or white, but her life is gonna change for the worse with Kunal telling the truth of this illfated marriage.
Abir chose a girl who he felt would help find solutions to relationships including that of finding his elusive father( i remember Abir telling Nanu Mishti will be able to find his father). Kunal was not given choice of finding the girl that he wanted.