RE: Raising stall speed?
We're not sure what you mean when you say the plane stalls at a very slow speed, but you need a headwind to get it to stall at that speed. Wind has nothing to do with it. If an airplane stalls at X mph airspeed, then it always stalls at X mph airspeed. A headwind makes the groundspeed lower, but airspeed is not at all affected.
If you cannot make the model stall when there's no wind, then there's something wrong with the flying technique. An aircraft in flight does not notice the direction of the wind, it only responds to changes, so if the wind is 10-15 mph, the model will only see changes of 0-5 mph, and only respond to the direction and magnitude of the wind changes. It doesn't recognize that there's a base 10 mph wind speed.
The problem with most model flyers is that they tend to land too fast. They don't take the model up high and play with airspeeds to find the best speed for the model on approach. You need to determine the proper throttle setting and fuselage attitude for the correct approach. That means you will have to find the proper elevator setting to give you the correct approach speed. Shoot for the end of the runway, and then you'll land a bit farther down when you round out and flare. If the model floats down the runway, you've made the approach too fast.