It's supposed to sound "məmbosankan", not "mɛmbosankan"
Sounds more like an ə than ɛ to me
Not it's not. Try it again
I see the root word bosan how does the "kan" identify the word boring vs. bored?
/-kan/ is being used to indicate 'causative'. Something is 'boring' because it inspires the feeling of being 'bored'.
I recall people saying "Aku boring" to mean "I'm bored" Which always sounded strange to me.