Oh Lara - major LES here! My heart just aches for Barney and for you as well. It's obvious from his video that he is fading, and he does appear to be quite miserable. The only saving grace here is that he still continues to eat. What a little fighter he has been.
I know that you are are torn between wanting him with you for a while longer, and letting him go. I think that all of us with fur kids have faced that same situation at some time in our lives. I don't have any doubt that you'll know when the time is finally here, and that you'll help Barney on to RB. My prayers are with you and Barney - for Barney to have a peaceful journey and final sleep, and for you to be strong!
Hugs to you both, and please give Barney a gentle little kiss from me on the top of his sweet little head!