Is there anyone else who could try explaining to your husband that you are still recovering from a serious injury, are in constant pain, cannot cope physically with the evening out he has planned, and to top it all have lost so much weight that none of your clothes fit?
He might just realise how serious things are if it comes from someone other than you.
If not tell him precisely what you have written here, and point out that all the Christmas preparations you have been making are done entirely because he loves Christmas, not because you really have the energy to do them.
If he pooh-poohs things, tell him that you are not going with him to the function, that you hope he can find someone who would like the ticket, then go to bed and stay there leaving him to cope with everything for the next two days.
When he asks when you are going to get up again, say, "When my back stops hurting so fiendishly, sometime next year, probably."
I cannot understand why your GP is talking about anti-depressants, you are recovering from a serious injury. I would see another doctor and try acupuncture to see if you could perhaps get some relief from pain.
Are you sure that the chairs you sit in and the mattress on your bed are suitable? I know a new mattress wouldn't entirely solve the problem of back pain, but it might help. Your physiotherapist should be able to advise about how hard or soft a mattress you need. If you aren't going to physiotherapy, get a referral.
I can't pretend to say whether your husband is totally lacking in empathy - it sounds like it, but in my opinion men of our generation haven't been taught to try and consider other peoples' feelings.
Please stop trying to be the perfect housewife. If he wants Christmas as it always has been, he will need to do the work.