Hi,
DD had this terribly when she was about 5 months old, and there were two babies the same age as your DS whilst we were there. DD was then in and out of hospital for two years before finally being diagnosed asthmatic and being prescribed the correct drugs in order to keep her out of hospital.
Coming off O2 whilst sleeping is always the very last thing to happen. The amount of times I have been kept in for an extra 3/4 days with a seemingly total recovered lively toddler bouncing off the walls because her SATS were still dipping whilst she was asleep!
Hope you are feeling better, now, I honestly know how shit it is, and how depressing the cabin fever is.
I'm sure you may be aware of this, and I really hate to be the bearer of bad stuff, but often after a young child has had a serious bout of RSV there is evidence to say they become much more susceptible to wheezing episodes/asthma. If they have a cold it is more possible for the cold to end in a wheezing episode or them requiring O2. Like I said, I really don't want you to think I'm kicking you while your down, but it is a good thing to be aware of, so if he does get a little cold you are ready for action if you hear a wheeze!
I know your DH can't come up, but I used to trade respite with other parents! Obviously only when the kids were sleeping, but we would just trade numbers and buzz each other if they stirred. Even just 15 mins MNing outside rather than is a hot stuffy ward made me feel much better.
I really really hope all your family is improving, and like some one said up thread, hopefully you will all be back to normal by Christmas.
Take care