Definitely get the neutering done now. It will help though it will take up to a month for the hormones to stablize.
It sounds like he is reprimanding you and usually that happens when a dog feels he is in control and the boss. Some males start displaying dominant behavior at puberty (around 7 months) but many dogs don't challenge their owners until about 18 months or so. They made do so unobtrusively by just not obeying as quickly or only obeying when they feel like it or when they might be reprimanded (training collar?). They might object when you do something they don't like or if you try to make them do something they don't want to do. When that happens they usually will give a warning like a growl and if that is ignored, they will nip and if that is ignored really steop up the reprimand. Now I don't know for sure that is what is going on but It may be especially given the circumstances.
I know you have kissed your dog for a long time but dogs do not like to be hugged or kissed or leaned over. Some dogs do not even like having their heads petted though most dogs don't mind that if you are not looming over them. It is something that all behaviorists and most trainers know and usually communicate to their clients. Read more on this here:
In addition, part of your dogs aggression issues may be due to a medical reason. Dobermans are prone to both hypothyroidism and to disc issues especially in the cervical (neck) regions. Hypothyroidism can cause sudden aggression and can appear to be for no reason. Read more on this here:
A thyroid panel will need to be done to ensure that a thyroid imbalance isn't the problem. They are prone to disc problems and since you were touching the neck at one point when he attacked and leaning in or over to kiss a cheek might have put pressure on the neck or moved his neck which may have caused pain from a bad disc. Read more about disc issues on the following pages.
Part of it may still be dominance based as well and stepping back up your obedience training should bring him back under control though I'm going to suggest a different method without using the collars. Training collars have their place and I do use them for long distance recalls, but prefer using a positive based training or a balance training method. So look over the following site. The following site is helpful in helping owners train their dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
Use a high value treat like hot dog slivers or raw liver. Each time a dog voluntarily obeys a command (even for a treat), it makes them just a little more submissive to the person giving the command. Right now, if he doesn't obey, he will get a tone indicating possible shock or a reprimand from the prong collar. While voluntarily it is also based on negative reprimands. We are turning that around and instead of reprimanding him, we will reward him for doing the thing we are asking him to do. This makes him want to obey and not be forced to obey. That does make him want to be more submissive to earn the treats. As he becomes adjusted to this new positive training, you will gradually reduce the number of paper thin hot dog sliver treats and substitute calm praise or a favorite toy as a reward. Always have treats on hand so he never knows when he will get them and when he won't. We use little pouches that can be carried on a belt or around the waste. Over time, the dog becomes submissive to the human voluntarily. As such it is the humans job to determine who comes in and what will be done or not done. The dog doesn't get to make decisions on what is allowed. Also the boss gives reprimands not the submissive members. Try this type of training and see if you don't notice a difference.
Definitely get the medical issue checked as I suspect they may be a contributing factor as well. I'd also not allow him on the furniture. Dogs that are allowed on furniture tend to feel that since they are elevated to your level or higher if on your lap, they mentally feel elevated as well in the pack order and thus are the boss. Keeping them on the floor can help lower them mentally back to a submissive position in the pack. Attach a leash and use it to remove him from the furniture. Give a correction in the form of a short tug to get his attention and firm "NO" when he attempts to get on and a treat when he starts not trying to get on the furniture. Thus you are providing negative reinforcement for the getting on the furniture and positive reinforcement for the desired behavior (not attempting to get on the furniture). It won't take him long to realize staying down gets him treats. Some people give a dog their own lower piece of furniture to sleep on which is acceptable.
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