Jealousy and insecurity is not the basis of their marriage, yes RK was insecure and jealous of Sultan, but Sultan played the trigger in getting RK to realise that actually he was in love with Madhu.
It made him realise his mistake and he did go about trying to sort things out with Madhu but he was unsure of whether she had moved on or not and kept refuting his efforts hence he resorted to his RK way of trying to get her to listen to him, and lets be honest it's how RK usually deals with situations, he's done that with Madhu on many occasions and Madhu herself has always made things difficult for RK when she is in angry mode, so there was nothing new there.
The added factor was the CV's deciding to experiment with a stupid triangle which seems to have backfired somewhat and hence why it makes Sultan's character look pointless which is a shame for AR because i feel he has great potential to play Sultan if they had stuck to his slightly sinister/mysterious persona.
Hopefully they can bring that back with the introduction of his Mother.
As for RK and Madhu, RK has reassured Madhu that he trusts her and their love and that he has changed his ways, now it remains up to the CVs whether they are being genuine this time or whether they want to drag this revenge/payback track further.
I for one hope they don't but you can understand why fans might be slightly apprehensive because we've so far dealt with 2 twists in the past both of which involved Madhu/RK and a mandap so 3rd time round everyone is still a little tense as to what might happen.
They are also shooting back to back it seems which means that CVs can pretty much change their minds on the track at a drop of a hat.
I do agree with a previous poster that RK/Madhu's marriage and union will always have a sense of foreshadow, they are meant to be yet not meant to be if that makes sense, and i think that is also integral to the story of M:EIEJ and the CVs have always stated that their love story will have many ups and downs to make it seem epic in true 'filmy/bollywood' style.
So I think we will see them married, but then their happiness may be short lived if Sultan is to play an important role in their lives.