Some very interesting DX there. Unfortunately, my players can`t handle these odd-format audio files (tried winamp, real, windows media).
It seems to me that quad and longwire are really not suitable for FM DX frequencies. I suspect your results would have been just as good using the built-in whip antenna only, with the advantage that you could quickly manoeuvre it to avoid interference and/or pick up maximum signal. 20 m longwire certainly is not right for FM band of about 3 meters wavelength.
The Es signals were probably so strong that they overcame the antenna wire anyway. One is entirely dependent on when an opening occurs, not so much with having good antenna gain.
Or a yagi cut for the middle of the FM band should give good gain and directionality, but I don`t know if it could be matched properly to that receiver. Perhaps you have already looked into how to do that with the quad, or maybe not with the bad results there.
Typical minimum distance for Es is about 500 miles = 800 km, and most common distance is more like 1000 miles = 1600 km, so you would not be getting nearby Bangladesh via this mode, but rather tropo (weather-related) or groundwave. Maybe parts of Myanmar are far enough away, and of course further parts of India and Pakistan.
With FM DX it is very important to be aware of the distances involved. It might be helpful to draw circles of 500, 1000 and 1500 miles around your location a map. Most of your Es would come from 500-1500 with a peak around 1000. Altho occasionally beyond 1500 is possible by multiple-hops.
So-called trans-equatorial propagation is another matter, which you also might get, outside the summer Es season. Signals are generally steadier but weaker and not fully quieted.
I am basing my comments on some DX I got in Thailand 40 years ago, and on lots more experience here in OK, 36 degrees north, about the same as J&K or northern Tibet, but at least not too far north of you and in the same hemisphere.
Good luck on planning your DXpedition, but if there is not a rather unpredictable Es opening, you may be disappointed. Of course the odds will be much better in May-July.
Or if you become aware of an opening, perhaps a rush trip out to the remote location.