<human>: Can you provide a brief rundown of the text in within 3 sentences?

I don't know if this goes here or r/dogs. Guess we'll try both.

We were together 3 years, recently broken up for the third and final time, and he's made it well known that -he- would be taking the dog.

Now I would understand under other circumstances that -if it was before we were together - he would obviously take the dog. But, I gave him 800 $ for the dog, the dog was 775 $ so it did more than pay for him. I put in the effort for training, and exercising the dog. I've bought him all he needs toy/treat wise to keep him busy during the day. Kept the yard clean, maintained his nails and coat.  Though my ex was there for some of it, the most he did during this time was take him for an off leash run every 3-5 months, pay for food (which was like pulling teeth, getting him to go 'out of his way'), and vet visits.

I'm the one that the dog listens to the most, the one he gravitates towards  (besides my Father, who spoils him), and the one who has
the best chance of keeping him happy through this change.

I'm INCREDIBLY fearful my ex will leave him in a crate all day, won't be able to keep up with his high energy, and my boy will be neglected. I can easily see him being pushed aside for my ex's needs and becoming very destructive/angry.

I don't know what to do to convince/persuade my ex to leave him here with me. I've told him I will let him come get him for a visit when he wasn't working, and that I wouldn't try and keep him from him. To which his response was, 'I'm not treating the dog like a divorce child.'

I really don't want to lose my best friend because we couldn't work out our problems. I feel as if my ex only wants him to hurt me, and I have no idea what to do.

Sorry for any typos, alternating between crying and having my dog try and lick my face.
<bot>: My ex wants to take 'our' dog, despite the fact that I put in the effort to train him, kept him healthy/happy, and paid for him. What do I do?