What should be my CAT percentile to get into IIM Indore if my academics is 83/82/7.7?

No, frankly your chances of getting admission to IIM Indore are very scarce. This is because its shortlisting criteria are as follows

As you can see IIM Indore lays emphasis on past academics a lot (almost 80%). Conferring your profile, the chances seem scant. Since you already lack the diversity factor and even the past academics are not up to the mark, the only way is to ace the CAT exam. Even a 100 percentile would not be enough to get selected. 

Since nothing is under your control now the best way is to opt for IIM Calcutta. This is because it’s the only IIM that gives little value to past academics. According to its criteria, you will score full marks both in 10 and 12. If you are an engineer a 99.6 percentile might get you a call. If you are a non-engineer it might be even lesser. 

So don’t get motivated, with a good percentile you can get into any top B School if not IIM Indore.