I think you're on the right lines. I'd probably go for the meaning of milk = eventually goes sour / scissors = eventually go blunt - which would tie in with the thoughts on futility you outlined above.
The line 'like a cheap squirting flower' is difficult - maybe fakery / unfunny / a bad joke
and 'like worms when it rains' - possibly meaning inevitable / always occuring and has connotations of death as well.
I think you're on the right lines. I'd probably go for the meaning of milk = eventually goes sour / scissors = eventually go blunt - which would tie in with the thoughts on futility you outlined above.
The line 'like a cheap squirting flower' is difficult - maybe fakery / unfunny / a bad joke
and 'like worms when it rains' - possibly meaning inevitable / always occuring and has connotations of death as well.
Great song whatever the meaning!