I think the quote on the bottom of Pomtzu's post says it all:
"The clock of life is wound but once, and no man has the power
To tell just when the hands will stop, on what day, or what hour.
Now is the only time you have, so live it with a will
Don't wait until tomorrow - the hands may then be still."
You have "lived with a will" with Barney and I think he's loved you for it every step of the way. This decision is heart wrenching, but you know in your heart what is best for Barney. He does, too.

Thank you for sharing him with us and know that God will be with you both to guide sweet Barney where he needs to go, to guide you in your decision, and to heal your heart in love. You have no regrets; you've been a wonderful and caring mom to Barney. Bless you!