‘adabana’ refers to a non-fruit-bearing flower, or ‘something that is flashy with no content’. Hence, ‘fruitlessness’ above. The ‘scatter away’ part in that line refer to ‘flower petals’, in case you don’t get the previous line. Also… correct me if I am wrong to recall that flowerless plants do not produce fruits. Kinda like a pun?

‘ikuseisou’ actually translates to ‘many months and years’, so this line literally means ‘The nights of many months and years that accumulated’. That’s kinda long, right?

‘rasetsu’ refers to a ‘Rakshasa’, a man-eating demon featured in Hinduism and Buddhism. I had half the mind to just go with ‘demon(s)’ for simplicity.