Sunil Sir, a few suggestions!
1. I think departure at 21:00-22:00 is ill advised as your trains will likely clash with Padatik, Darjeeling mail and all those plentiful nightcruisers that start from Sealdah Division then. My advise would be to re-route via HWH-BDC-BWN instead of HWH-DKAE-BWN.
2. A BWN halt will be needed so will be a GMO or PNME halt.