Don't feel guilty He has a great home and will come around eventually. Of the four dogs I've raised, only one has had bad separation anxiety, the rest came around quickly. What I found helped was not making a big deal about coming and going out of the house. I had to consciously remind myself to not pay attention to my dog for 10 minutes after I came home. The reason for this is, if I said my good byes and hellos, the dog "knew" it was a big deal I was coming and going. It's hard, but after the excitement of you coming home has worn off, you can go have fun and give him attention. I'd also mention this to your neighbor who checks up on him. Every hour may be excessive and may be enforcing bad behavior despite your intentions. A crate or xpen would provide safe assurance while you are away. I would limit it to once a day if you absolutely had to.. but again, your neighbor should not make a big deal. Also while my dogs are pups, I confine them to a crate (or xpen will work too). This is not only for their safety (who knows what they can get into while I'm gone for the day), but also to provide a safe space for the dog to feel at home. From the moment my dogs come home for the first time, I try to make the crate a fun place that they can feel safe to retreat to and relax. I give all meals, toys and treats in their crates in the beginning. The one with separation anxiety is coming around. She used to bust out of her crate daily. She chewed through plastic crates, bent and bit off wires from wire crates, and warped wire crates so badly that I had to zap strap all around the crate and use leash clips as extra enforcement on the doors. But now she runs straight to her crate for meals, or if I have something yummy in my hands that she wants, she runs in and waits for it there. You can feel free to provide puppy safe toys to keep him busy. Our go to are kongs. My dogs can empty them out quickly now but if I plan ahead, I freeze meat or peanut butter so it keeps them busy a little longer.

Hope that helps!