Alpha status is really a straightforward thing to a dog as it universally understood and accepted. People find it very hard to grasp the concept and even harder to put it into practice for, I believe, two reasons. The first is the way we view our pets - we all know that we have domesticated wolves living with us. That bit is easy to understand. What muddles us up is that we are suprised by the intelligence and individual character of the dog and we fall in love. This would be fine if we continued to see the dog as a dog and treat it as a dog (wolf) but humans find this very hard. Instead we start to treat the dog as part human and give him, for instance, a bit of cheese as a treat when we are making a sandwich for ourselves, or encourage the dog to sleep on the bed with us. Dogs are dogs - that is it - that is as hard as dog training gets. There is no other concept that has to be remembered. Dogs don't think like humans or talk to each other like humans or understand our actions or gestures as another human would because they are dogs. Dogs can not be expected to take care of themselves on a busy street because they don't understand the human world as a human does.
Which brings me on to the second reason - terminology. Words like dominance, submission and aggression are very strong and emotive words when humans use them. Every one of them is linked to violence, fear, danger and threat. When used correctly in the context of behaviour they have very different meanings (usually...there are exceptions but let's not confuse the issue now). Many people find the idea of being dominant towards their dog a very difficult thing to deal with as they are imagining forcing, making the dog do what I say or hurting the dog to make it comply. Many trainers are also guilty of misunderstanding the subtle submissive gestures given by their dogs and are not happy until the dog is flat on it's back.

In the wild the pack will sleep where the Alpha pair decides they can sleep. If it is cold that may be in a heap that looks like a jumble - it isn't! Every member knows exactly where the limits are and do not overstep them. If you allow your dog to sleep with you because you and he both enjoy the closeness you are telling your dog that it has an equal rank, status, level of dominance as you when it is bed time. This is fine if this is the only time your dog gets this message and you are happy with it. It is not fine if you are having any other problem with your dog as it will confuse the dog and make ironing out the other problem more stressful and difficult for you both.

By allowing Cody to sleep on your bed when you are not there you are telling him that he is second to you only. That is also fine if you don't mind, if he leaves the bed EVERY time you ask him to and if everyone else in the house doesn't have a problem with the dog. But I would suggest that second place is still very high for a dog that has had a hard time trusting you to lead him.

Phew!!!! You should know by now that if you ask I will answer.....fully!
Hope that has answered your questions without putting you both to sleep!!!!