Object guarding is a delicate issue and resolution depends on a number of factors. We have a number of products to help but there are a few things to keep in mind. If you kennel or crate your dog or provide him with a place that is "his", we'd suggest feeding the dog in a neutral area. An immediate resolution is to feed the dog by hand for basic tricks, obedience or games. If the dog object guards routinely, we recommend the following titles and the assistance of a behaviorist that is in your area.
Separation anxiety of stress can lead to a variety of behaviors that can become problematic. Of course we want the dog to be comfortable, stress free and occupied positively when you're not around. A few suggestions include playing some music, providing an item with your scent and an interactive toy such as a Kong toy or Busy Buddy can keep a dog mentally occupied and stimulated during alone time. We also recommend Stress in Dogs by Martina Scholz and Clarissa von Reinhardt.
We feed our dogs a combination diet depending on season, schedules and travel. Most of the year our dogs eat a raw diet and we believe the benefits are well worth it. Digestion, dental health, coat, energy and even smell can be improved with a raw diet. There are many premium kibble diets as well and for many owners they are a great solution depending on schedule and availability of raw ingredients etc.
Housebreaking is about schedules and consistency. We recommend utilizing a crate for housebreaking and establishing a schedule for feeding, potty breaks outdoors and play time. We have used the techniques in and now offer, How to Housebreak Your Dog in 7 Days by Shirley Kalstone. This is a fantastic little book with sample schedules and great information and considerations for housebreaking.
Often, difficulty with grooming in general is a low threshold to minor discomfort, lack of trust or confidence. Sometimes it's the opposite- a dominance issue, an issue of personal space. Move the dog to a quiet area that is 'neutral'. Patience is the key, remain calm and make steady progress. Gradually desensitize to handling the feet. Don't rush getting the nails trimmed the first few sessions. You can easily handle the feet and activate the trimmers without actually trimming the nails and praising the dog and offering a food reward for good, calm behavior. Allow the dog to smell the clippers and make time in the area positive. You can eventually trim a nail gently but don't worry about doing all the nails in one sitting. Understand it will take some time and be patient. You can do the nails over a period of time until it becomes less of an issue.
Trim the tip only being careful not to cut the quick. You can try a Dremel tool as well to take the edges down without the clipping motion of traditional clipers. Some dogs mind the Dremel less although some habituation to the mechanical sound may be necessary. Don't be rough or scare him, take time to make the dog comfortable. Invest in good clippers, sharp clippers are better and result in less pull on the nail.
This is not an easy problem to correct. Dogs that put their heads down during motion are usually pulling very hard on the collar and are not really looking for the owner. They are frantically trying to move forward as if they knew they are going somewhere and must get there fast and at all cost. They have a lot of energy and feel compelled to pull and run. Sometimes they smell the ground because of the smells left behind by other dogs or in an attempt to pick up the scent of the owner. It is very hard to determine what he is really doing without seeing him in person but here are some possible corrections.
1) If the dog pulls hard to get to the owner who is in full view of the dog. Try conditioning the dog to a whistle or specific noise that he associates exclusively with the owner. You can do this by sounding the device as the dog eats every day. During training the owner hides far enough away for the dog to have to lift his head to try to look out to find him. Placing another "decoy owner" at the opposite side with an identical device will get the dog's attention at both ends of the ring.
2) Handler training is also crucial. The handler should not reward the dog with forward motion when the head is down. He should stop and have owner get his attention from afar and then take a few more steps with the head up. Anytime the dog's head goes down the motion should stop.
3) If smells are what is distracting the dog (males who are very territorial tend to smell a lot) you may use some some "vicks" ointment and do a quick, light swipe of the mint formula on the dog's nose. He will be unable to smell anything for a while.
4) Sometimes the issue is not one of behavior but one of structure. Dogs who are "loaded in front" tend to move with the head down. The term applies to a variety of issues. Restricted front reach and a very ample, sweeping rear tends to make the dog fall forward. Low withers does the same thing. Sometimes a steep croups causes the energy to be delivered to the front quarters in a downward curve. Heavy fronts such as dogs with deep chests can also add to the problem. Structural issues are even harder to correct.
I am guessing that you have more of a training, than structural problem. You must go slow, in short sessions, demanding good performance and rewarding the correct posture every time.
Canine Training Systems has many series of videos dealing with dog training. Although it is not directed specifically to correcting "show problems" the concept of canine psychology and how to mold and change behaviors can be applied with some creativity. Particularly the obedience sessions taught by Ivan Balabanov can shed great light as to how to shape the posture in small increments.