The "blonde man" has covered the trailer floor with motor oil and upon leaving, sets fire to a curtain, which in turns causes a massive explosion. If set fire to, motor oil will burn, but never explode. Only flammable liquids which vaporize, such as gasoline, would result in an explosion. Even then, you would have to build up a significant volume of such vapor before a massive explosion would occur.
When Allison is in the shower, the water turns off and almost immediately the curtain opens and Allison steps out with a dry towel wrapped around her. There is no way she could have been in the shower with a towel wrapped around her and it stayed dry, and there is no way she could turn off the water and wrap a towel around herself that fast.