Sue and Desley: your replies really helped, thank you!
I'm can see I'm expecting too much from the poor boy, and you're right - six weeks is nothing. I can be impatient without realising it sometimes, but I'm just impatient to see Bruce settled and happy. He's been through a lot, bless him, and he hasn't really asked for much. (Best of all, he accepted straightaway that Drum is top cat!)
Will try the food bowls again, but for longer. Will keep him on the Zylkene. He started his higher strength Vidalta last night, so I'm hoping his levels will be normal soon and he feels better.
Definitely in it for the long haul, he's a lovely lad!
BTW, there's a cat tree upstairs, which he's explored the lower levels of but isn't too fussed about. There's no room for one downstairs, unfortunately.