What he is saying is what I pointed out just yesterday, the IA needs MRSAM and QRSAM. Both are highly mobile batteries and can be placed anywhere. Although he has mentioned SPYDERs, those will be needed to protect the IAF's ground assets. LLQRMs like SPYDER do not have the range to cover everything, hence the need for the army's equivalent. QRSAM are built to be operated from forward areas, like the radar design has been made with particular emphasis on mobility.
However the issue with the S-400 is it can pick up and engage aircraft flying at high altitude, which are typically AWACS and EW aircraft. If force multipliers are forced to operate at lower altitudes, then the surveillance ranges will reduce drastically. Both Brahmos and KH-31 will be critical in dealing with the S-400.
And yes, the inventory of 1300+ Hellfires with the IAF is going to be extremely effective. IA will get its own fleet of 6 Apaches with 270 Hellfires next year. About 1000 among them are capable of fire and forget, and can be used like the way mentioned in the tweet. I bet more can be bought and used from existing American stock whenever we want to. Hopefully the IAF has asked for immediate transfers of more helicopters.