partial hysterectomy, false heats, demodectic

Hi there. my 7 year old 1/2 greyhound 1/2 yellow lab has been battling the mange and the swelling with occasional discharges for 3 years. 3 years ago she was ravenous with her skin and was in a bloody life-threatening situation when I started injecting ivermectina weekly and when that stopped functioning, dectomax. the local vet had a difficult time diagnosing her and many things were crossed off the list. she's had food allergy, heart worm, and mange tests of scrapings, blood, fecal, and diet. She has full body mange and the number of hardened scabs is increasing. She is susceptible to intestinal parasites. She is not well and is worsening. We live in the tropics next to a river and beach with another dog which seems to be well. The floors are of cement tile and I throw down bath towels as bedding. Her towels are soiled through her skin and her smell is mild rotten eggs. Last couple days she's thrown up once just before dinner laid down a minute then got up and ate her dinner. This morning she tossed a cup of chow at the back door. I'm told that if a dog has mange it is usually the symptom to a large problem (cancer, heart worm,..). Could that problem be the partial hysterectomy? What do I do about that? She had three injections of estrogen a year and a half ago but all it did was initiate the onset of the swollen vagina and discharge. I'm attempting to treat her mange with borax and hydrogen peroxide, her intestinal parasites under control with a central america brand Pramectina prazicuantel and ivermectina, but i don't know what to do about the smelly licking and slurping accompanying her false heats. The biting irritates her skin and everything is working in unison, against her. Her energy is waning and although she's loving and good spirited I can see the hang dog slouch and gate, the dimming eye sparkle, and her changing skin. She was robust when we moved into this house 3 years ago. I got her off the beach in michoacan mexico and noticed early on that she had spells of the hang dog slouch and gate. I've had her since she was six months old and had her fixed at her first heat by a jungle hack which almost killed her. Its been a rough road been and she's loving, loyal, and intuitive-like intelligent. The heats?