Usage in these examples.

1. The reasons supporting the rise of veganism are developments on those explored through vegetarianism – the idea that animals are not simply commodities for human consumption and exploitation.

2. Heart disease can be a medical emergency, a delay in diagnosis and management can lead to loss of the life

3. The villain had a scheme to not to rob Fort Knox but to eradicate it – thus increasing the net value of the villains gold stocks.

4. The compound was huge with poison gas vents – a big room designed to be used only once.

5. The film explored new age culture, especially concerning the future – for this is truly a movie about surrealistic visions.

I'm sure 4 is a noun phrase, but I'm not sure about the other examples?

1. feels to me like it should be in brackets instead of a em-dash ?

2 & 4 look similar but 2 is a comma splice right as it's a complete sentence?

I'm not sure about the other examples: Is 'thus' and 'for' conjunctions in these examples or starting dependent sentences?