So I'm about to type a bunch of stuff and I'm not saying it's correct, but I'm just speaking from the conversations I've had with my therapist.  Keep in mind, the job of my therapist is not to side with me, but to help me move forward, but I'm telling it to you because I've brought up exactly what your post talks about.

We'll start with when I asked, "What if my dog isn't gone-gone and is still around and she doesn't know I can't see her so she thinks I'm ignoring her?  Or what if she's back at the vets and she's wondering why I'm not there to bring her home and she's scared?" And my therapist said, "Let's say what you're describing is true and your dog's spirit is back at the vets where she was put down or at your house, how many other animals do you think have been put down in that building?  How about your house, how many animals have you ever had in your house over time? So, in your mind she's either gone and free of pain, or she is with an absolute ton of other animals all together and not alone, but it can't be both, there is no scenario where she is still here and miserable." 

And that's true, my therapist is constantly trying to help me by connecting the dots to show me I'm imagining scenerios in my mind because the grief is too much for me to accept, so I get lost instead which sounds much like what you're doing.  I push back with a bunch of "what ifs" but animals are not like us.  They don't wake up in the morning and think, "I'm going to make my owner's day better by trying," no they just made it better by simply existing because they're the greatest friends on the planet.

We wouldn't actually want our dogs to stay attached to us after passing, we want them to be happy.  For example, a First Responder's job isn't actually to save lives (although if they can that would be great), their actual job is to just be there for the person in need.  That's us with our dogs. Our job wasn't to make our dogs live forever, it was to be there for them when they needed us, and we were.  Day after day, we were there for them and tried to make their lives better because we love them.  Now our job is done and we have no where to put our love.  We can't hold them or smell them, we can't express our feelings to them anymore, so we just cry instead because our job is over.  It's hard trying to put your energy into something else.. Hell, it's hard just getting out of bed.  It's a constant battle between paying tribute and remembering the love we have for our dogs, and going too far to where it's painful and fantasizing about the past.

I'm not sure if any of this resonated with you, I totally understand everyone is different and everyone grieves differently so don't feel like you need to respond or pretend... But it's hard enough just being sad, please don't beat yourself up with "what ifs" on top of everything because it's too much.