Partition has nothing to do with the economic lagging of states like WB. 32 years of communist rule is to be blamed. Actually the current dispensation is not any good either. Bengal is stuck between the devil and deep sea and will continue to stagnate.
And Punjab is not where it is because of the Khalistan movement. But because of their adoption of the Green revolution and their hardwork.
Partition had off course played it's role along with communism, we lost our natural hinterland and had to accommodate millions of refugees(no offence to them, my grand parent were one). Communism ripe best in social disorder, why do you think Bengal which had been historically Congress stronghold and always had an array of bourgeois become communist all of sudden?
Green revolution doesn't come cheap, you have to build an world class irrigation network, just check out the amount GOI invested to make green revolution a realty. Yes I agree mentioning Khalistan was bit theatrical.