No.
A switch does not use wattage, or consume power which is a better way of putting it. It depends on what appliance is being controlled by the switch.
Some rooms have an outlet controlled by a light switch at the door. This is normally in bedrooms. It is possible that the switch is wired to only one of two outlets in a duplex outlet since it is easy to configure a duplex outlet to separate the bottom and top outlets.
Plug a lamp into a working socket of an outlet to ensure the lamp works. Then turn off the switch and plug lamp into all outlet sockets, top and bottom outlets until the lamp doesn't light. Then turn on the switch and the lamp should light. Often a switch in a bedroom is only connected to one socket in a duplex outlet. It is possible to remove a jumper in an outlet to isolate the sockets for just this purpose. Often an electrician will install the outlet upside down (The third prong pointing up, to identify the outlet.
Could be a loose connection somewhere, or a bad switch, or a bad outlet.
because the lights are not controlled by the ignition switch; they are controlled by a separate light switch.
If you mean can you plug a radio into an outlet controlled by a light switch, the answer is yes, provided the radio does not draw more current that the circuit can supply. (This would not apply to your standard household radio, but only to a high powered unit.)
Sure. For a light you need a fixture to hold the light and the light itself. The light needs to be connected to a voltage supply which you can get from the outlet. In the outlet box you will have a black, white and bare ground wire. Essentially you connect the white and bare wires directly to the light and switch the black wire (hot) through a switch.
Break off the tab that jumps between the wire mounting screws on the side of the receptacle. This turns one receptacle into 2 seperately controlled parts--one is always hot and the other is controlled by the switch (the one with the lamp plugged in).
A single pole switch controls a light or outlet at one location. A 3 way switch controls a light or outlet from 2 locations.
You can attach/splice into the power feed to outlet (ways of doing this can vary with how the outlet is wired but make sure that all or part of the outlet isn't controlled by an existing switch). You can then take the hot, neutral and ground to a light fixture or to the first switch, then to the second switch. It is normally easier to do this project by taking power to the light (s) first, with 2 wire drops to the switches, from basement or attic.
Change the wall outlets
No. A light switch merely allows energy to pass, or not to pass.