Behavioral issues with dog

Hey all, hope this is allowed. For some background, my husband and I have had our pitbull for a little over 2 years. We adopted him from a shelter at the age of almost 8, so he is now almost 10. Things were great at first but we started to realize he was was not a fan of any sort of strangers, he will go after anyone he doesn't know. It's been hard to have our families over when they are scared of our dog. This dog also has the worst allergies I've ever encountered in dog, I feel like he's constantly in pain of some sort. We've been to the vet numerous times to try and get medications adjusted/allergies tested and nothing seems to help. He's now started to become more aggressive with my husband and I and we are now parents to a 6 month old. We had a discussion with our vet about the possibility of euthanizing him and I feel like the worst pet owner ever to think about it but I know I have to put the safety of my family and I first. I guess I just need to hear we are doing the right thing with moving forward with the euthaniza.