I'm very sorry to hear about your dog, he must have been truly beloved by you and your family.
I would think that the time you've already spent with him would be proof that you cared, and you loved. I hope your dog rests in peace, free from pain and hurt. I'm sure he knew that he was loved dearly.
It's always difficult, losing a loved one so suddenly, but I think you'll agree with me when I say that I never regretted having loved them, despite all the friction or mistakes or regrets and pain that comes with it.
We've lost several rescues before this, most left suddenly, almost without warning too. Some deteriorated slowly, and we had to make the call. We keep mementos of them around. Photos on our devices, tattoos, illustrations, their toys passed down to the younger ones. My sibling hung the collar of one of our rescues in the car's dashboard. She (the cat) used to love travelling and car rides. She's not here anymore, but with her collar, we can still take her on trips with us.
They can be a painful reminder of course, but for us it is also a proof and reminder that yes, they existed. We loved them, and they loved us. We want them to be a part of our life, still.
I hope you'll be able to express your longing, love and regrets and find some closure yourself. Whether it is through your creations, or finding a way to keep him with you and your family. I hope you find the time to grieve, and I hope you'll find some peace too.I'm sure you loved him very, very much, and I'm sure he does too.
Thank you so much for taking the time to play and comment, I really, really do appreciate it. Once again, I am sorry about your loss, but I'm glad that this opened up a conversation.
Much love, and hugs if you need them <3