It makes me sick to think he checks on the dog (every 10mins) more than he checks on us (his wife and kids).

I'm sorry you are going through this. I hope things get better for you soon, one way or another.

I have an acquaintance in that position, and i would happily boot the other without a second thought if i could.

Thoughts are with you.

Is he having an affair?

If you think of it in ANOTHER way, you might feel better about that. His constantly checking on the dog is an admission on HIS part that the dog is a brainless ditz, who MIGHT aimlessly run out into the road, or eat the children's toys, or even his own poops.

Conversely he respects you and the kids enough to know that he does NOT need to constantly check on you to know you aren't doing anything enormously stupid.

Dogs are super dependent, and stupid sometimes. They get into trouble constantly. Humans are not so inclined and can be left alone without nearly as much worry.
Besides, kids follow mommy around, don't care what dad does. That has been my experience.

...

Sometimes you need to step away to observe and make a rational decision.In my opinion its just a temporary phase .

No words