
I've got a rescue Terrier who I've had for 18 months now and he is exactly the same as your dog. This is only my own personal experience but Copper has been through every training regime I could find and he is the same now with other dogs as he was at the start. It's an ongoing struggle with him and I believe that he will always be like this to some extent, attacking and biting other dogs. I almost never let him off the lead as his recall is zero, although with no distractions (i.e. other animals) it is very good.
I have a hint from your post that this dog is getting on your nerves? (not a critcism, mine hacks me off too at times). I would love to walk for miles with my dog scampering at my side and behaving in what I would call a "normal" manner. But the reality of it is, he won't and probably never will. I've decided I can deal with that, I'll walk him on the lead. If the dog's behaviour is irritating to you then you might be giving those vibes out to the dog, which won't help. I was giving nervous vibes to my dog when we were out and it was making him worse.
I have no doubt that the dog will have a great life with you but you may have to accept that he may not do what you expect of him and a huge amount of time, patience and effort will be needed to change that and dogs can be very stubborn. At the end of the day you might decide that he is not suited to you and your situation, in which case that might be the time to move him on.
I really hope you decide to keep him - mine can be a right royal pain in the backside but he's worth it in other ways. Good luck with what you decide :)
CG