i understand your fears... my oldest dog (at the moment) is 10, but back when she was 3 or so, she started to become dog aggressive and aggressive toward animals in general. she killed 2 cats, it was devastating. she is a large pit mix (some have speculated mastiff type), and i was concerned and afraid, so i hired a "professional" behaviorist who guaranteed she could help. not only did she NOT HELP becuase she was afraid of the dog (who had NEVER been aggressive toward humans), she had no working experience with pit type dogs, especially the "gamey" ones like my dog, and she was a dingbat. she went so far as to send a letter to my vet saying that the dog was dangerous, that she was "very concerned that the dog lived with a child", etc.. she recommended that i rehome or euthanize the dog. i was HORRIFIED. i had to call the vet, in tears, and explain that my dog was not a danger to my child.. i had nightmares that the child welfare folks would show up at my door and take my baby
that never happened, for the record. anyway, i found a GOOD trainer after that debacle who helped us tons. Marleigh is old now, has "raised" 3 human babies, is a dream with the kids, and (while she still does not "like" other dogs and would love to chase all the fuzzy critters) she has been trained to have self control, follow commands and is living a happy, fulfilled life in our home. i debated rehoming her, but i discovered that the only people interested in a large dog aggressive pit dog were scumbags, and i was afraid for her safety in their hands. she was MY responsibility from the moment i rescued her, and had a home been available with decent folks who genuinely would have cared for her, i would have taken it. but it didnt happen. we worked through the issue, and its still work years later. but i dont regret it a bit. you will find your way in this, and itll be alright, i swear
