I typically use a much higher spawn to sub ratio. More like 1 part spawn to 2 parts sub just because it is faster and the faster you get full colonization the lower the risk of contamination (IMHO).
Since your container is outdoors, it very well could be a sub moisture issue although being outdoors FAE seems like it would be as good as it gets? Has it been dry in your area lately or are you getting sufficient rain? It does not take much to change humidity outdoors and it changes constantly which mushrooms do not like. That and insects are the reasons why I grow indoors. You have very little control over the growing environment outdoors unless you use a greenhouse.
I am up in the air as far as casing goes. I am trying casing for the first time right now and so far I can say it definitely helps with sub moisture retention and deterring contamination. I think it also has to do with what your current species likes as well.
This is all just my opinion though, I am no expert.