Probably already solved, but here is the solution:
You can grade in HDR-no need to make a DV pass, yet.
Take the timeline once done and as you are grading in a scene referred environment it should just convert to P3 easily.
Then you do a little offset. India projectors are 12ftl that’s why your offset needs a bit more power.
For IMAX you can give them the normal P3 DCP render. They will do the rest.
All IMAX are done at PrimeFocus in Mumbai. You can also ask them if you have any doubts.
Additional info: Imax has to accept the film first as it works on a revenue share basis. If they say yes, then it will go to the IMAX cinema.
good luck