Hi, Barbara. Your problem is that you have sealed the house up so nicely that the humidity can't escape. The water condenses on your nice, cold windows and runs.
There are probably 3 problem areas that you should address. The first is the basement. Just put in a dehumidifier. If you have a damp basement, you should search the board for other ways to solve this problem like sealing the walls and getting the water to drain away from your house.
The second is the bathroom. A few showers can really put a lot of water in the air. You need to install a vent with a fan in the bathroom ceiling and exhaust the humid air to the outside. Depending on where you live, you might have to wait until spring. Climbing on a snow covered roof is very dangerous. Don't just exhaust the humid air into the attic as this will cause even more problems. Have the fan wired so it comes on anytime the bathroom light is on.
The third area is the kitchen and this cause a lot less problems than the first 2 areas. A range hood with a vent to the outside will cut down on humidity and also allow cooking smells to be exhausted. Hoods that just "filter" the air and recirculate it will do no good. You have to get the damp, smelly air outside so the same warning about the roof applies.
The storm window salesman was right and deserves credit for telling you the truth. Storm windows will create some dead air but are not sealed well. Double pane windows with an inert gas between the panes will do a lot more to prevent heat transfer. Aluminum window frames transfer heat a lot more efficiently than wood or vinyl. The glass in your window doesn't transfer heat well either but you do not have enough thickness to make much difference and the glass has a large surface area. When the budget can stand it, you might want to look at more efficient windows that replicate the look of your original wood windows but even that will not be much help if you don't get the humidity under control.