Concerning status, you will only get EQM if you fly Jet Airways on an AA flight number.
If you are flying on a Jet Airways flight number, as you noticed, only some fare codes earn miles, but none of those miles will be elite-qualifying, only RDM. K fare on Jet Airways earns no EQM and earns no RDM.
So you would be better off with BA, unless you are looking at an AA flight numbers, which I don't believe exists on Jet LHR-CCU.