Had the vet over again yesterday. After just over a week, Perry is putting some pressure on the leg, but still not walking on it (putting it down when he stands and putting pressure on it, but not even pressure). Plus, a day or two ago I started to hear it crack/ pop (once or twice when I moved him and a couple of times when he moved it). It sounded like the knee to me. Quick google search said possibly related to cruciate ligament (but he doesn't have any pain which is generally associated with that), meniscus, luxating patella OR it could just happen (sometimes things crack).
The vet examined it more, did feel the cracking (but can't figure out exactly where it's from) but is pretty sure it's not the ligament or the patella (it wasn't moving at all as she manipulated the leg) and despite not using it, when you manipulate it, it isn't causing any pain at all.
So, end result - still not exactly sure what's wrong, probably still a muscle strain (though I am not sure if that explains the cracking) AND she's said we're probably looking at 8 weeks or crate rest.
I also have to be more diligent on keeping him on a tight leash when he's out of the crate. He's doing fine in his crate, no fussing, no whining or barking. I want to be able to let him out more, but whenever he's out of his crate - on his leash, sitting beside me on the couch with a pile of toys - all he wants to do is run and jump around - this is where he ends up whining and barking, etc. The vet doesn't have any light sedatives which could chill him out - all she has is the ones that knock them out for 8 hours or so (can't remember the name - but it's the ones they used to use when they would sedate an animal for travel).
I just hate him being in his crate for 20+ hours a day. I'm not convinced he's getting enough water (though I moisten his food and I can tether his leash when I'm in the kitchen so he has access to his water bowl there, but he will dump his water dish if it's in his crate so can't leave him water all day), we can't really do any training and I think he's sliding backwards on his relationship with my husband which was slowly improving. So, I'm feeling guilty and incredibly frustrated.