Dobermans coat & behavior

Question
I have two questions regarding a three year old male Doberman that my husband I adopted from a shelter two years ago.  First of all, because of apparent skin allergies, i.e. dandruff and hair thinning, we started feeding him Nutro's Lamb and Rice formula.  This appeared to correct the situation but about 6 months ago, the dandruff returned and we once again switched his food to the Diamond brand.  This initially seemed to cure the dandruff problem; however, within the last 2 or 3 months his hair has been thinning along the sides of his back.  He also has dry skin under his arms and in between his legs and has developed horrible body odor.  We assume this to be a dietary issue and we're wondering if some sort of fish oil supplement would help the problem.  He does like to lick his dry skin a lot, which we try to discourage him from doing.  
Secondly, while the dog has been generally well-behaved, he is starting to display a tendency to purposefully urinate or defecate indoors when we have house guests over because he doesn't receive all the attention.  What is the best way to discourage this behavior and/or the best way to discipline him when he does relieve himself indoors?

Answer
This sounds like it could be hypothyroidism,which does cause a lot of coat and skin problems,as having a weird body odor-so it will be a good idea to call your vet,and ask for the dog to have a thyroid test

This is one of the most common problems in dogs-but it is also easy and cheap to treat,although it is for life,they have to take pills

Also skin infections will present the same symptoms,but again only a vet can treat that

The bathroom problem is probably something else-the best thing to with that type of problem is to see a trainer,as this is a problem with him trying to be in charge of everything,and can it could get to the point to where he might want to bite people,so it is good to nip it in the bud right away,also a trainer might want to see the dog so they can show you how to fix the problem