I know in rice too much nitrogen is bad. It causes lodging (plants get too heavy and blow over) and increases the chances of having insects and disease problems. No idea what too much does in baccy, but I'm sure there is a happy medium somewhere. It probably wouldn't be too bad to start easing off the closer you get to harvest. I would think with the lower concentration you are using now it wouldn't be too strong to countinue using for a few more weeks - just going with my gut not any documented protocols so I could be wrong.
Reading the first few links knucklehead sent it sounded like they were cautioning against muriate (Cl) of potash (K) = (KCl), which goes along with what knucklehead said about chlorine and smokeability.
I'm sure you've heard before, but just to say it in case it helps anyone else - if you have a fireplace or fire pit save those ashes and leavings for mixing into your soil early next year - they are like gold. They make a good source of Potassium (K) and trace elements and help raise the the Ph of the soil. The early tobacco farmers were all for the slash and burn method for starting a new tobacco field.