Boy, to me it sounds like he crate phobic or has separation anxiety or both - especially since you say he has been doing this for 5 years. Their are some people on here that can maybe give you pointers on what to do in this case - in particular, Quercus, as she is a trainer.
To me, it doesn't sound like you have a crate that is too small - although if he is crate phobic, I don't really know. They don't require a big crate and of my 3 basenjis - 2 prefer a smaller crate. My girl Ruby used to have accidents in her bigger crate (36x23x26) and when I switched her to the next size down (sounds similar to your size - mine are 30x19x22), the accidents stopped. And since your dog stopped pooping in the crate, it sound like you made the right move going down a size. Have you ever tried one of the plastic vari-kennel types? One of mine prefers that over the wire crates (I use the blue & white medium size).
Have you ever tried leaving him uncrated in the bathroom with everything up out of reach - has he ever destroyed any woodwork or anything like that? And what about moving him back into the kitchen in this new house and gate him off the kitchen from the rest of the house?
The only other thing I would add, is when I was having separation anxiety issues with my girl Ruby, I ran her on my bike everyday before I left and I would also walk her to make sure she was really tired by the time I crated her - it did seem to help - although it didn't help every day.
I would definitely not recommend leaving him out for 5 hours with no one around - especially if it is separation anxiety as he could end up digging out of your enclosure. I know there are some on here that do it - but I think they have doggy doors.