First of all, I don't think the issue here is sanitation either. That said, the rest of this thread is a mouthful, so please bear with me.
I think the first thing to do here is to make sure you're using good water (i.e. NO Chlorine/Chloramine). Just because the water tastes good, that does not necessarily mean that it's good to brew with. Search the thread on here "A Brewing Water Chemistry Primer" by Yooper I think. Try brewing a proven recipe, once, using reverse osmosis or distilled water following the directions in that thread. It dramatically improved my beer.
The second thing is temperature control. The issue here is, fermentation produces heat (especially more aggressive yeasts). It might be 5-10 degrees warmer in the fermentor than ambient temperature in your chamber. This creates two problems. At the peak of fermentation activity, you need some way to suppress the temperature to keep it within the temperature range the Yeast prefer (i.e. A chest freezer). The second, and possibly more important issue is, you want fermentation to end AT OR ABOVE the warmest temperature the fermenter reached during fermentation, so you need some way to heat it. This can be done using your little space heater, or placing the fermenter in a warmer ambient temperature than it was held at during fermentation (moving it to a different room).
The reason this is important is because, as fermentation slows down toward the end, the Yeast are no longer as active, therefore they are not producing as much heat. At this point, the Yeast start to transition to cleaning up off flavors they left during fermentation, rather than consuming sugars. Since they are not producing as much heat, the temperature of the fermenter drops and this can cause Yeast to stall and drop out. If that happens, they won't be able to clean up those off flavors and you will notice it in your beer. It will generally just come across as a "rough" or "unrefined" character.
I think the first thing to do here is to make sure you're using good water (i.e. NO Chlorine/Chloramine). Just because the water tastes good, that does not necessarily mean that it's good to brew with. Search the thread on here "A Brewing Water Chemistry Primer" by Yooper I think. Try brewing a proven recipe, once, using reverse osmosis or distilled water following the directions in that thread. It dramatically improved my beer.
The second thing is temperature control. The issue here is, fermentation produces heat (especially more aggressive yeasts). It might be 5-10 degrees warmer in the fermentor than ambient temperature in your chamber. This creates two problems. At the peak of fermentation activity, you need some way to suppress the temperature to keep it within the temperature range the Yeast prefer (i.e. A chest freezer). The second, and possibly more important issue is, you want fermentation to end AT OR ABOVE the warmest temperature the fermenter reached during fermentation, so you need some way to heat it. This can be done using your little space heater, or placing the fermenter in a warmer ambient temperature than it was held at during fermentation (moving it to a different room).
The reason this is important is because, as fermentation slows down toward the end, the Yeast are no longer as active, therefore they are not producing as much heat. At this point, the Yeast start to transition to cleaning up off flavors they left during fermentation, rather than consuming sugars. Since they are not producing as much heat, the temperature of the fermenter drops and this can cause Yeast to stall and drop out. If that happens, they won't be able to clean up those off flavors and you will notice it in your beer. It will generally just come across as a "rough" or "unrefined" character.