Dog advice

Hi so , in the middle of the pandemic I moved in with my in laws because I lost my job. They had found out someone’s dog had puppies and were ready to give them away. My bfs mom (let’s refer to her as my mil) had mentioned mentioned she wanted an inside dog because she was lonely but that was before we moved back in July 2020. She ended up picking out a puppy and we brought him home in August. I had just lost my pup in feb so I wasn’t ready for a dog which is why I didn’t pick one out. Immediately after bringing him home, my bf and I went shopping for the puppy. We bought him dog food, clothes, a bed, toys , etc. fast forward to today he’s pretty much mine and my boyfriends dog. He sleeps with us , comes to us, cry’s for us. He doesn’t care to be with my in-laws much. The only thing they have paid for is for him to be groomed a few times. At times, while I’m away he kills the water he has and when I get home there’s no food or water in the bowl. I brought it up many times this has happened. I solved the problem by buying him a bowl with the tub thing so he always has water. My bf and I want to move out this month and Idk how to politely ask for him. My bf and I have jokingly asked for him and shes said it her dog. I am prolonging us moving out because I CANT leave him. He filled a little hole I had and love him unconditionally. My in laws have been nothing but amazing to me so I don’t want to be mean but I want our dog. Advice?