1) Please get your vet to check if it is mange or not. Better go to a good vet. Have a case that a friend was cheated by 3 vets and the mange turn to secondary stage. Pity the dog. Signs as dandruff and flakes can be mange.
2) Bath with Malaseb for this and also use frontline to clear the ticks. Use some anti tick solution for the areas around you.
3) Get it checked if it's bacteria infection or some infection or not. If after a few treatments still not ok try changing dog food. A brand to recommend is Natural Balance Fish and Potato. This might be food allergy if you want to detect it you must feed strictly on this diet and no treats or whatsoever other food.
4 & 5) Dandruff and flaky skin might be mange(high possibility) or some skin prob get it checked. Do not let your dog go near other dogs.
Last time don't have one don't know why suddenly got so many problem. Scare my poodle will get the infection also. Have to quickly bring her go to see doctor. Will let you know again