My condolences and complete understanding on your pain and loss. It hurts to lose our friends especially knowing how much you love yours. There is no big meanie in the sky testing or watching. And christians are not worried about animals to begin with anyway.
If there is a god he knows nothing of pain or what is going on here in this fucked up world.

Forgive yourself, if you hold any guilt, you did nothing but the best for your babies and they know it and they are still loving you and you them. So often people in grief also hold so many "what ifs". It holds true in my business, when human pass, and it holds true when our furry friends pass, because we love them as much.
Your babies were so fortunate to have you all to love them. And anymore pets that allow you to come into their lives will be as lucky.
So I think that if there is a god, where we find him would always be in the love shared and not the pain. The writers of the bible just wrote it from a purely ego point of view, which brings in selfishness and pain. (And sexism, and racism, and cruelty etc). So organized religion keeps us trapped in a pretty screwed up illusion of a god. (I think you yourself have mentioned the speech Matt Damon's character gives the nun in the beginning of Dogma in a past blog...way back.)
But I don't think this is the time to discuss it, I think this is the time for you to take care of yourself and grieve. If you ever need to "talk", and someone to shut up and listen, hit me up Josh.
 

"And christians are not worried about animals to begin with anyway. " My whole family is Catholic... I, my mother, my husband etc... care and worry about animals. Not every christian is closed minded or the exact same. Not all Christians believe the exact same thing, it comes down to interpretation.
I believe there is a god, but i didnt for many years. My brother died... he was in my moms womb, ready to come out and the nurse inserted the needle for the saddle block into HIS side right IN HIM. Killed him quick, my mom felt him roll knowing there was something wrong with him then... and nothing, no heart beat after that... she got to feel her son die minutes before he was born. We got to hold him, this 6 1/2 lb little blonde haired boy... got to see how beautiful he was, and we all saw the hole in his side...
They were supposed to send an autopsy, they refused and no matter who we got involved we still got no where. First it was outright refusal to give it, then it was "lost" so we could never see it. My mom didnt know what to do and was too stricken with grief to push anything. NOTHING ever came of it... these people should have paid for what they did as far as i am concerned... and god at that point didnt exsist to me, not for years. I have to believe in something in order to get up each day and try. If you dont believe in god that is fine, it is your right to believe what you please...
I am sorry for what your going through, i dont deal with death well, and i love my animals... my mom lost 3 pets in 2years time... her 3 fav. pets she has ever had in her lifetime, the dog she lost we never found his body and he was like a kid to her. He was only 5, the 2cats that died... one had neurological issues and was we were told mentally handicapped basically... i didnt know something like that could happen to a cat, but it did. he was only 4months old when he died. (in my house on my daughters bed at the time) the other cat had issues (he was dumb as hell, nearly to the point of the 1st cat) but no neurological stuff... he got cancer and died at 1yr old. Sometimes it seems when it rains it pours... bad shit happens one right after the other. I hope that things get better for you, and if you ever need to talk or someone that will just listen... write me. I have been through some major hell in my lifetime, i can sympathize.
 

I have ranted about got like this to. I once burned a bible to see if I could get his attention because I felt he was not hearing me. Real angry person then.

You said it your self that you take the hard to place ones, the ones that need the extra help. You do this because you have the love and the means to do so. Not alot of people can or will. Weather you have them for a week, a month, or a year you have given them the most greatest gift that they will never forget you for. And that is love. You took them out of a shelter and brought them into your home and cared for them. None of us are garenteed anything. You are very special for doing this. I work in a shelter and yes the ones that need the extra help get pass over for the healthy ones. So no matter how long you have had them for you gave them what they needed, and that was love. We get in animals all the time that I know that they will never make it in to adoption. I take care of them and I love them and do what ever I can to make them comfortable. And yes it hurts alot when they are gone. But I never regret it. And I will do it everytime. Because like you I care. No matter how much it may hurt me, the hurt and suffering that some of these animals come in with will not compare to mine over loseing them, so I will continue to open my self up to these animals so that at least they can leave this world knowing that someone cared and loved them.

Hold on to the good memories of them and they will live in your heart forever.