Legg Perthes is extremely painful. Even if he is not limping all of the time, it does hurt. I have had a few fosters who have had the surgery and they have done very well.
I do strongly suggest that you see a board certified surgeon for this. I was at the vet hospital one day and had a conversation with a lady who had a regular vet do this surgery and the sciatic nerve was severed. She was at the specialist for answers on this. Very sad...I don't know what ever happened to her pup. It is a relatively simple surgery, but I would still only use a specialist.
After the surgery, there really is not a lengthy recovery period. It is not like surgery where there are plates and pins....there is nothing to "undo" so to speak.
They do limp for a while after the surgery. I have one right now who is about a month out from his surgery and he does use his leg now unless he runs...then he lifts it. That will resolve with time.
I would definitely ask for some meds for him until he has the surgery....and I would do the surgery as soon as I could. A consult with a specialist is definitely something I recommend.
As for the crating concerns, I have not crated the ones that had this surgery and all was just fine! But...you should ask the vet about that as well.
Good luck and welcome to YT.