I´m married to a veteran myself and I can relate to a lot of the things you wrote about in your posts. You´re feeling frustrated, lonely, scared, angry and all the rest of it, and all those feelings are completely understandable, as living with a spouse who´s got ptsd can be a true nightmare. I think you were spot-on in saying

"I'm not sure where the PTSD ends and the person begins",

which obviously means that you already have a good idea about what you´re dealing with!
Unfortunately, you cannot expect too much activity nor initiative from him at the moment, as he´s got his hands full. I know, living with a full-time couch-potato isn´t easy, it can drive you absolutely nuts.
You´ve received some good advice/opinions from people here, and hopefully you will find some strength in yourself to "put up" with some of your husbands faults for the time being, as he is indeed very unwell and in need of professional help. It´s positive that he is in therapy and although no changes are going to occur overnight, that´s at least a start.
Remember that you´re not alone!