1st of all a very nice post :)
I have just finished watching last week's episodes & after watching them I reached to this conclusion (which may sound alien to you) that may be Harshad was never a really bad guy..I'll tell you why I think this way.
Being Aliya's brother,he has known them forever thus knowing their weakness/Strength isn't really big of a deal.
I dismiss the idea of him being a part of Fab 5 or the "Band of brothers" ever.I'd like to believe he was always an individual who alone was able to take on the Fab 5.However things started worsen once he & Mukti broke up..& in this case too I believe the reason being the fab 5 themselves.
Remember him telling Mukti while twisting her hands " your hands are still soft only if you could become a li'l" or to Manik " Last time that I checked she was much more stronger than you" It somehow gave me a vibe that he was emotionally very much connected with her but somehow things didn't work out coz Mukti has chosen her friends/Band over him...
or may be he just simply made them taste the taste of their own medicine by using Mukti while Mukti had fallen hard for him .
Him using Dhruv & Navya-Is wrong but still one can't just blame him for that..The reason being :
Navya " Enemies enemy is you friend"
Dhruv - Attack the weak point of your enemy..& For Manik it's Dhruv..
About the pairing - I don't want to think about them coz I'm still unsure what I want...while Dhruv Nandini click the most with me,for a fact I know that the end game 'd be Manik Nandini..so yeah..