I am so sorry for your loss of Doolie! When I first read the thread, I was so hoping he'd recover but, based upon his early life, I guess it's not a surprise.
THANK YOU for all your kind devotion to him. This is what they all deserve, but what so many of them never get. His life with you was paradise - no bird could ask for more.
As to getting another bird, consider this - it in no way diminishes the love you have for Doolie, nor disrespects his memory in any way.
What it does do is help to diminish the pain you have at his passing, and afford another deserving bird the opportunity to benefit from all the love you have to give.
In many ways, it is the finest tribute you can give to his memory. Please, do consider getting another bird to nurture and love. There are many out there, they all deserve it, and you need & deserve to have another wonderful bird in your life.
I, too, have a sort of "tribute" spot in my house, to honor my furred & feathered loved ones I've lost. It's poignant, but it also brings back fond memories of them and, in a way, ensures they're always still with me, at least a little.
I guess I'm rambling a bit here, but you need to know we're all behind you, and we all thank you for all you did for wonderful Doolie. Many of us have been through this, and know (and share) the pain you're going through.
Take heart, you've done everything right, and know that Doolie loved you as much as you loved him.