Need help with a really bad body odor. Any ideas of what we can do?

I hate asking this question, but I really am all out of ideas.

My FIL has been with us now for three months almost. We have a number of issues which we are getting through and resolving, and somedays things are actually going ok...! (4 bad days, 2 good ones, 5 bad days, 3 good ones, so we do have some progress)

The biggest issue however is the smell. He has such a very bad body smell that it is taking over the entire household, and just walking past his bedroom is enough to make you gag. The smell is also in his clothes, which are really old and mangy. We are replacing them slowly but not all at once (although I would love to) as I know that would stress him out completely. He is 90 years old.

What I have done so far is:

* Wash all his clothes twice: first with vinegar and a bacterial antiseptic, and then with regular washing powder and softener.
* I wash his clothes separately to ours
* Changed his soap for an antibacterial/antifungal especially designed for old people and those with sensative skin
* Wash his sheets every second day with vinegar and normal washing powder (as above for his clothes) and air out his blankets and spray them with antifungal spray
* Clean towel every second day ( feel like I am running a laundry service!)
* trying to gently cleanse his colon/ digestive tract with gentle healthy eating

It is not a sweat smell but an acrid sour/rancid smell that burns the nostrils and turns your stomach. I have read that skin cancer can smell, but not like this. (he has one or two spots, but nothing bad at all). We were in the chemist the other day, and people actually moved away from him to go and stand in another queue, because the smell was so bad.

I light candles, spray room freshner, use febreeze around the house, have lemon oil burners, and in my office I light incense .. but the smell is all pervasive and overpowering.

Any ideas of what we can do? This is not one of these things that any of us can "just accept", it is becoming a real problem, as we cannot have anyone around to visit, the kids won't bring their friends home anymore, and I can't keep up this laundry pace for much longer. It feels like I am chained to the washing machine!

Thanks in advance.