Bleu Boy has not had any issues what so ever that was a direct result of his AAI surgery. It was the best decision we have ever made.
I would say this ..
How long do you want Pete with you .. 10-15 more years relatively speaking? It is not too late I would personally have the surgery and get him out of the pain and let him start a joyful life with you . A friend of mine her Bailey had the surgery and was not casted like BLEU BOY and she did fine. If you are worried about the recovery do not be because that is easy. Once you are through the surgery it is easy street from there. MY ONLY COMPLAINT WAS it took a year for BLEU BOYS HAIR TO GROW BACK.

Financially speaking there are tons of options and we all can help you with that as well.
The main thing I was scared about was BLEU BOY was so small. You have a great advantage with PETES size and weight. Pete would do fine because his bones are formed and sound. BLEU BOY was a 6 month old pup 2.5 pounds and his bones were so soft. This is a advantage for you that PETE will do just fine.
I understand how you say he has had this for quite sometime but...................regardless in my opinion I know a lady with a SHIH TZU same weight and year as PETE and her SHIH T ZU is now enjoying a wonderful life because she went through and got the surgery