There is a fab website called itsaspringthing and they have cockers on there too. Have a look, the forum is very helpful and will point you in the right direction, and you will get support too. You will also be able to read other peoples spaniel problems and realise you arent on your own.
It sounds to me (although i may be very wrong) that your cocker is somewhere near if not the top dog, and you are coming lower than him in the pack.
There are lots of ways to quieten your cocker, but am a bit unsure as to offer advice incase it is the wrong advice for you and him.
I have taken on a 5yo springer who was noisy when we got him. He wanted to be next to a human all the time, wanting lots of attention. He has another dog friend here. He has calmed down considerably in the noisy demanding department through a bit of trial and error and consistency from both me and my OH and the same treatment from anyone who comes into contact with him. It was hard to start with and i wondered if i had taken on too much with him, but have seen the light with this problem and now am onto the next.
I believe the cocker is harder to train than the springer and needs more mental stimulation too, and often will sulk with its owner until it gets its own way.
As for the lack of sleep, gosh thats got to be hard for you,I need my sleep or i get grumpy and dont function well at all. Maybe you have someone who can give you a break from him so you can get your hed down for a while. Having a rescue or puppy is like having another baby. Hardwork but In my opinion, well worth it.
I hope there is some thing in this post which will help you. Keep us posted, I'm sure the support wil be here in some way or other for you.