Oh, I see. That's kind of interesting. I can't remember a vet telling a caregiver not to use diapers (belly bands) before. Maybe she wanted to be sure you got in the habit of always expressing and did not simply rely on a diaper?
Really don't know what the thinking was.
Many dogs (it sounds like yours is one) need diapers even when completely expressed at bedtime. Some dogs dribble 24/7. Some dogs can hold it for a few hours but not 8 hours. On a positive note, it's good if your dog is running plenty of fluids through his system, because that will help prevent UTI.
A diaper for backup will help keep him dry to avoid a urine burn on the skin, and avoid having to get up in the middle of the night all the time, and reduce the need for frequent baths. (Though he looks like he'd fit in the kitchen sink, he's adorable!)
It can be hard to tell what causes a UTI, but a lot of times it is incomplete expressing, especially during the first weeks when you are still getting good at it. It happened to me with my dog. The second week after her surgery, she got a bladder infection. I had been expressing her bladder very conscientiously, but she got the infection anyway simply because I wasn't very good at it yet.
I don't know if this is an option for you, but do you have a table you could put your dog's crate on? Having him up at waist level would save you getting down on hands and knees to change blankets in the middle of the night when you're not moving very well. The only thing is, you have to be careful to latch the crate every single time, even if you just turn your back for a second. You don't want him rushing out excitedly and doing a nosedive off the table. If you have kids, I'm not sure putting it on a table is safe (in case they forget). The ideal place is somewhere that the dog can see out a window during the day (as long as he won't be in direct sun at any time). I have a back problem, too, and up on the table was way easier for me to deal with. Here is a picture of my dog in her crate on the kitchen table.
Oh, by the way, another issue with the crate on the table was I had a large cat name Teddy who liked to jump up on top of the crate and it would move a little when he did. You can't really see it, but I got some big C-clamps and fastened one on the table on each side of the back of the crate, and that kept it from sliding. If you need a picture of the clamps, let me know.
Hopefully if you can get him on gabapentin or another medicine for neuropathic pain (the pins-and-needles feeling) and get the right dosage, then he won't need the cone and will be able to move around inside his crate better.