One thing has struck me in your description of your dp. He sounds very fearful of the pain, and in particular of making it worse. That's natural, of course.
I have chronic neuropathic pain (though not in my back) and this has really struck a chord with me. I'm sure some of the harsher posters on here would think I was lazy; I work only very part time, and although I do much of the housework, I don't do it all, even though my dh works full time.
Chronic pain is tiring, debilitating and depressing (clinically depressing, that is). It just is, and bad attacks of pain are so so frightening.
But the solution, as far as there is one, is not to stop doing everything.
I did a pain management course, and my life is much improved. I'm still in pain, a lot of pain, but I now have a life too. I have learned to pace myself, but still get stuff done. I've made myself do some exercise, and learned that this may worsen things in the short term, but in the long term it helps. I have learned to control the panic the pain sets off, and I can now do more around the house, and have more of a social life.
It might be worth encouraging dp to ask again about pain management. What they suggest is sometimes obvious (but still good advice) but sometimes less obvious. For example, I've asked my family not to ask how I am, because that makes me focus on the pain unnecessarily. But there are loads of other pieces of advice / wisdom out there that the pain management people can suggest, as well as looking at the medication he is on.
I'm not going to comment on your dp's laziness or otherwise as I don't know him. But I'm sure you'd all be happier if his pain was better controlled.