Sorry, you cannot daisy chain Bluetooth devices like the way you described.
That is you cannot do this: Echo Dot --> iPod --> Bose speaker.
If you connect your Dot to the iPod, then your music will come out of the Dot. If you connect your iPod to the Bose, then your music will come out of the Bose.
If your goal is to have voice control over your music, you can accomplish this by using an audio cable to connect to your Bose. But keep in mind that Dot doesn't know your music and there is no way for Dot to know what's available on your iPod. So you will not be able to say "Play xxxxx song by xxxx artist". You will only have basic control like with any Bluetooth device, such as Play, Pause, Skip, etc.