I have a male ****terdale. I think the first thing worth mentioning is what you are experiencing with patter dale ownership is pretty normal and not worth getting stressed about. Stress and dogs do not mix, especially highly strung dogs.
It sounds very much like you have given the dog a huge amount of scope at a young age. We've all been there, usually because we want to get the dog going and we want the assurance that the dog is capable before we embark on competency - the training part. Usually this leaves you training out problems you've already put in. Your three goals ARE achievable, despite what a lot of terrier owners might say. You will just have to put in more work in some areas (steadiness) than say a lab owner might. But your terrier will come equipped with a lot of field craft and drive that a lab would lack to the same degree. The first thing I would recommend is withdrawing all uncontrolled stimulus from his life. Keep him on the lead do not let him form an association with prey that does not involve you. This is not an instant fix, but when the dog is older you will find him far steadier and the difference between a dog which charges through woodland bumping rabbit after pheasant and disappearing into the next post code when the deer you were there for gets out of his seat.
The first thing you should understand about any dog (terriers in particular) is prey drive. Prey drive will dictate your dogs life and most decisions he makes. what is important at a young age is to understand that dogs will always specialise to a specific prey. So knowing what you want the dog to do the most is a must from a young age. Switching between different types of work can be difficult, not impossible, but difficult. You're also less likely to have an 'obsessive' dog. Dogs specialise in the prey which is easiest for them to obtain. Think lurchers have speed on their side so little furies are easier for them than retrieving ducks from water. A big thick coated lab who has built a relationship with the gun finds it easy to retrieve from water but would have a lower strike rate on rabbits alone. It doesn't mean there can't be cross over but I am sure you understand the principle. It stems from nature (using your attributes to expend as little energy as possible to get the most food). Because deer are such large mammals- ie a lot of food. All breeds of dog will be willing to expend substantial energy on hunting one and therefore to us display a larger prey drive towards them - think Fenton scenario pet charging deer with no encouragement.
With deer dogs this can make our lives very easy (or difficult for a lot of dog owners where chasing deer is either dangerous or undesirable). You might want to read up on tracking practice and get yourself a good harness and lead. you don't want the dog tracking scent off into the distance as well as bumping deer it could be dangerous for him. you also want a connection with the lead so you can read the dog and therefore the scent. you will begin to learn the difference between a cold scent a hot scent a gap a turn and different scent conditions. If your dog does need to bay or bring down a moving deer you can release him once you are close and can assess the situation, importantly with a small dog the size of the deer.
If you want to focus on steadiness then you need a consistent approach. make him wait for everything HE WANTS, his tea, getting in the motor, going through the gate etc etc. Make him wait, use a lead, he gets to do what he wants as a reward for steadiness. This can transfer into your tracking training and by how you introduce him to work. you can also use this same approach to unsteady behaviour to train out 'undesirables' once we have him steadied up a bit we can take him towards livestock on a lead under control and distract him with one of the things we have trained and reinforced him to be engaged with i.e his favourite toy covered in scent. without the risk of him pelting off after some woolies. once we have secured this focus on the job in hand we can start to trust him more around livestock and gradually progress giving him more scope (longer line, closer to stock) until we are confident with his behaviour. But first the behaviour needs to be stopped in its tracks, USE THE LEAD, it doesn't make you look like a bad dog trainer its a useful tool and important for a young dog. Ultimately you need to be responsible and if you **** off landowners by chasing stock your stalking and shooting permissions will very quickly dry up.
Finally the pining is a trait of the breed. It isn't impossible to get him to stop, this is achieved by working on steadiness in very small increments, keeping him focused on the instruction. you will find it harder with the breed as vocalisation is a trait bred towards, you will also find it a useful trait at times trust me!
A long response I know but I hope you find it helpful. If you can focus on one thing it should be reduce his exposure. This will also help him become obsessive about the traits you want when you slowly encourage them and control his exposure to them.
