Sorry
I am truly sorry for you and for Linus. I guess before I can give my point of view, is he in pain? If so how bad? Ask the vet these questions before you consider the decision. I think that if it's bad and he can't do any of the things he needs or likes to do then the best course is a humane end to his suffering.
If he is still able to eat, groom, recognize, and interact with you without severe paint then I'd think that it's not wrong to have a few more days of friendship. No mater what you decide, your pet will love you still and will forgive and accept you like it always has. True unconditional love is a rare commodity and pets, well, they seem to be the best of all of us at it.
Ask your vet about house calls for the final visit, most good ones do it now. It's a lot easier on the animals a sort of last nap on the rug by the fire place in the arms of your foreign thing. A trip to the vet is not what I want my pet's last memory to be.
As for the loss, perhaps nothing but time will ease your pain I'm afraid. I'm 37 and have lost a few, and I still miss them all. However, if I need a lift, the pictures of the good times we shared, and the fond memories of love and friendship can cheer even the deepest of foul moods. Perhaps your beliefs in the hereafter and life cycles may help you, maybe even a new friend to love is in order.
I think I learned a good secret from my first love, Whiskers, a small mutt found in the parking lot of a grocery store. I was seven and she a few months. A cross between a Dashoud and a Terrier, she was over long and with short legs and a shaggy black and white coat. Friends from the start, she helped me get though my parents divorce, puberty, and even my first broken heart. She always knew how I felt. We'd play outside from sun-up to sun down sharing everything, racing home and sharing a hasty meal before we'd set off again. Well she got old and much too fat (a result of my over sharing). Her favorite was licking the ice cream bowls and catching popcorn in the air. As I grew my time with her lessened but it was still quality. Some of my fondest memories are of the naps we'd take together after school my senior year. I come home and plop down on the love seat and she'd nap on my chest for a half hour or hour and then wait by the door until I came home tired and on the coldest nights she'd sleep under the covers with me and keep my feet warm. I joined the Army and after a few months of pouting in front of my door she became my Mom's new pal. Shes lived for until after my 25th birthday, to a ripe old 14 years. I was heartbroken when I got the call from my Mom, (I was too cool to cry then...) but comforted when I was told that Whiskers just wasn't living well, she was blind, and only had like 5 teeth, and on my last visit before she left this world she didn't recognize me. I think that's what did it for my Mom. Anyway I'm glad I didn't have to make the call, spared of yet another responsibility by good old Mom, but that's another story. However, oddly, that was not the end of our relationship together.
While I was devastated by her loss in the end she brought me a comforting message. I couple of years later, my best friend came to me again. I was a grown man in my twenties, serving my first tour in the Army at Fort Bragg. As I slept that night in my bunk I had a dream, the most real and moving I've ever had, and I remember every detail still for it moved me so. I t was and is perhaps the realest, most vivid and moving dream I've ever had.
She came to me and told me that she came to play with me one last time, but that she couldn't stay long. She said we could run and play like we did when we were kids. So we played...we played again down by the old creek behind our place. It was a perfect sunny Summer day, us both in our youthful prime, running, playing in the water, and chasing squirrels. In the end we stopped on the bank and sat together, sharing a lunch of a peanut butter and jelly sand which, smashed as usual, a few pieces of candy, and some water from the cowboy canteen I always carried. She took her last drink of water from my palm and began to walk away. I don't know if it was too painful for her to say goodbye but I stopped her. As I cried the cry I denied myself before, She told me that she loved me and always will. Her final thought was...don't worry, we'll se each other again....and I believe we will.
Do what you think is right...you will know when it's time to say goodbye. Whatever you decision you make Linus will respect it like he has any other.
Take care and remember the good times, laughter, comfort and life lessons you both shared....