Someone's taken my dog, it's a long story. Help?

Let me start from the beginning. Back in May, I had a dalmatian wander into my yard who i recognized from three houses down the street. He was filthy, underweight, and acted like he didn't know where he belonged. I took him in, gave him a bath, and posted an ad on craigslist saying I had found a dalmatian. I put up ads at the local dog hotel, the vet offices, the feed store, and talked with everyone in my small neighborhood to find out if anyone was missing the dog or knew where the owners were. No one had any idea, so I left a note at the house and kept the dog with me. I contacted animal control, and they said that I can either turn the dog into them or after 30 days it becomes mine. I didn't want to take the dog to animal control because I didn't want him being put down. After a couple weeks of having him, he was coughing really bad so I took him into the vet. They found out he had double ear infections and was strong positive for heartworms. We paid for his bloodwork to be done and we've been having him treated monthly getting him ready for his first injection, which is a week from now. After learning this, I knew there was no way to take him to the pound because he'd be put to sleep. Anyways, we've been taking care of him the past six months and on October 1st, he went missing out of our yard. I put an ad on craigslist, called animal control to let them know I'm missing a dalmatian, and put up signs, talked to all the people in my neighborhood like I had when I found him, and after 5 days got a phone call telling me they had seen the dog a few houses down from them. I went to that house only 3 miles away, and it was my Pongo. I ran into the yard, homeward bound moment, he was so happy to see me. The guy was like "so i guess you've been taking care of him". I said yeah, told him I couldn't find the original owners, apparently this guy, and he said he just umed the dog had found a home, that when they moved the dog ran off and didn't come back when they were leaving. Wtf? He said his mother in law drove down our road, their old road, and saw the dog and called him out of our yard to get him. He had his collar on with my dog tags that I had made for him, and when I saw him that day they had been ripped off (the metal was still there, just no tag). He said the dog was always an outside dog and that he keeps him tied to a tree during the day while he's gone and brings him in at night now because the dog cries outside. He didn't take me very seriously when I said the dog had heartworms, but anyways that's not the point of this post, I know i'm a better owner because it only took me 5 days to locate my missing dog because I gave a damn. This guy just so happened to find his dog after 6 months by happenstance. Anyways, I called animal control and told them the story, they said it's a police matter but they are on my side. I called the police, and an officer came out and talked to me, then him, and said it's a civil issue, that an animal control officer has to make the decision. When I found the dog, like I said, animal control said after 30 days of being missing that the dog is considered abandoned after that point, and whoever has vet paperwork (that would be me) is the owner. Does anyone know where I can find laws regarding this or do you have any advice? I miss my dog. It'd be different if it was a couple weeks after I found him, but it's been six months. I already have two spoiled dogs, I honestly wasn't financially ready to take on a third or pay for heartworm treatment, or another monthly Comfortis pill, another leash, collar, bed, more Taste of the Wild, more rawhides, but this dog stole my heart, like they always do. He didn't know how to play fetch, how to play much at all, how to chew on a rawhide, any tricks. Now he shakes, gives hugs, rough-houses, and can roll over. I really just need to know what laws apply to my situation. Thanks for reading!