He had dug himself deep into a hole with no one way out that felt safe or even possible.
Reading about your H's thoughts when he was away reminded me a lot of my H. That is exactly what he said to me at the beginning when he was thinking about coming home... that he loved me...that he was scared that he had dug himself a hole that was too deep to climb out of...that he was more sorry than he could possibly say...and extremely ashamed... didn't want to face anyone...didn't think he could...and was scared that things would come up daily that resulted in him feeling bad because he wasn't there or did something wrong, etc... A few weeks later, after making the decision to stay gone, he brushed his comments aside and said he was just "trying to fill some holes he knew were there". Didn't really get that explanation but I guess it made sense to him. I don't buy it. I think that it was the first time he looked in the mirror and came to understand what he had done and he was horrified and beyond scared and that it was just too much to face so he had no choice but to keep on digging and try to at least salvage his R with his kids who are thankfully oblivious to the things that he did.
