45 years and I never killed a dog or pup using motor oil, but I've never poured any down their throat to see how much they could take either...
I'd say the hook worms + infection had more to do with the pup dieing than anything else.
If a pup going hairless while on a good quality feed and in a clean environment isn't a sign of a poor immune system I don't know what is.
Many people treat the mange and think they have it fixed but it will come back AND it will be passed on to pups, maybe not all will show it but it will come back with interest paid down the road and then someone else will have to deal with it.
Dogs are a common host to mites and one that cannot live without being over come by a common bug is not one to procreate from...
On ear mites, we use a mix of mineral oil and iodine in the ear(must shake the mix up as it will seperate), or a couple drops of ivomec in the ears, both need to be work in the ear by rubbing the outter back side of the ear against the front between your fingers.
Having mites is usually noted by a dark wax coming from the ear and the hound "headshaking" or scratching at the affected ear. Sometimes it is a fungus infection in the ear common to hounds, the ear will have a "smell" to it. This caused by moisture and the ear being covered by the earflap makes an excellent environment for growth of fungus.