1. I'd use full strength, but just less of it. I would expect better longevity that way.Originally Posted by Eau Boy
2. I'm not sure. I doubt it.
3. The two enemies of fragrance as I understand it are light and oxygen. I'm sure keeping it cold would help it keep longer. Decanting might accelerate degradation through oxygenation. I'd recommend decanting for personal use only into a small atomizer for short-term use (http://www.essentialsupplies.com/ has a 10mL frosted glass atomizer. Just search on 'frosted' it should be on the first page of results). Personally I think freezing is too much effort for me. I keep bottles in the original boxes to protect from light.
4. No experience there. I think I've seen some 'imposter' websites, but they were people reproducing discontinued, classic fragrances.
5. If you're going to worry about that, you may as well give up cars. Statistically an auto accident is much likelier to kill you.
Hope this helps