Sir I dont think there will be any advantage if you board from NJP.Because I know the people from Bhutan prefer either APDJ/NOQ for catching long distant trains.But as I've already mentioned you about the uncertainty of the passenger trains running in the Dooars Route,I would suggest you please finish your work as soon as possible on the DOJ,get down from the hills,reach Jaygaon & take a bus for ALipurduar.That bus will make u reach to either Alipurduar Court/Alipurduar Chowpatty,from where NOQ station is easily accessible.Otherwise if u insist on travelling in train,try to reach HSA station before 08.00 pm & take the Intercity Exp for APDJ.I think,how much ever delayed it is ,it'll surely make u reach before ur desired time,so that u can catch Garib Rath easily.