1. He may demand a ransom which will take care of his short term money needs. Knowing Shyam he may volunteer to take the money to the supposed kidnapper to look look in front of the family
1a. This will strengthen his hold on the RM members as they will think he is willing to put his life in danger for the family
2. He needs to get the will changed and so killing him does not make sense
3. Well knowing Shyam he needs to gloat about his achievements (him fooling Arnav about Khushi) and other stuff as well which will lead Arnav to the truth. I mean according to the spoilers Khushi will tell him but he may not believe her
4. Khushi realizes how much Arnav means to her
5. Khushi saves Arnav
These are some ideas on the top of my mind. Please add to the list
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