our cat just died

Question
Hello.  I am really at a loss here.  Our cat of almost 4 years old just passed away 1 1/2 days ago.  Stanley was a 3 legged cat that my husband picked up at a job site.  The other guys were going to kill him because he had only 3 legs and didn't have any home to go to for warmth.  We took him in and eventually Stanley lost 1/2 of both of his ears and part of his tail due to frost bite.  He weighed about 15# and was 1/2 indoor and 1/2 outdoor cat.  He loved being outside and always came in for breakfast or supper and then would sleep the rest of the day or night away.  My two boys (ages 8 and 5) and I simply adored Stanely.  On Halloween afternoon Stanley came home and was walking funny.  He came in the house, I picked him up to see what was wrong and he had a big bruise on his tummy.  I took him to the vet the next day and they said he was going to be sore for a while and could hardly do anything to him because his whole back end was very sensitive.  
Last week (one week later) I brought him back because he wasn't eating and would urinate on himself so I was giving him sponge baths daily.  after an injection of cortizone, Stanley was back to himself, climing up stairs and wanting to be around us for love.  After a few days, the old Stanley returned, not eating and not having any bowel movements.  This past Sat., he was shaking all over like he had the chills so I called the vet again who gave us some oral meds to take for one week.  He said if that didn't work that we'd have to "figure something else out".  I knew what he was talking about.  By that night he was doing a little better, but still not completely himself.  He ended up going into our staircase and staying there until Sunday night when he was out far enough for us to pull him out the rest of the way.  When I got him in my arms, I knew that he was going to be gone soon.  I cleaned him up and told our boys to say their good byes to Stanley as i didn't think he would last much longer.  I was up with him until 11:00 that night and when I woke at 2:15am, Stanley was gone.  I wanted him out of the staircase so he wouldn't die alone so I brought him to our bedroom for some peace and quiet.  I told Stanley that it was ok for him to go, that we loved him and would never forget him (sorry about being so sentimental, but I really loved Stanley).  We buried him in our back yard last night and have vowed to have a perennial in our yard just for Stanley.  My boys are doing ok with his death, but now and then break up about it.  I am trying hard to tell myself that he died naturally, and that he wasn't in that much pain, but I am afraid that I let him suffer longer than I should have.  Those are the thoughts that torment me when I think of Stanley being throughout our house, laying on furniture, floors, meowing at us when he wanted food or just wanted attention. I can't get those thoughts out of my head on how I probably should've had him put to sleep instead of prolonging his life and pain.  Any suggestions?

Answer
I recently had to put my dog to sleep.  She had an osteosarcoma in her cheek bone, and I too struggled with whether or not I was prolonging things just because I couldn't bear to let her go.  Though the situations are a little different, I can certainly sympathize with what you are going through right now.  It sounds to me like you did everything you could...you sought medical care for him, and were very attentive to him.  Having assisted with many euthanasia's I can tell you that pets always do better when their owner's are present, and its all the more easier when it happens in an environment that they are familiar with, so I'm sure it was much easier for him given that he was at home.  It will become easier, and it's only natural to question yourself at such a time, but I do not think there was likely anything else you could have done.  My deepest sympathies.

Amanda