Cascade 220 Superwash Wool
might be your perfect yarn.
It is a wool and it is washable. And warm. Lots of colors to choose from.
I wouldn't worry about laundering the blanket. I'd just toss it in the washer on gently cycle, put it in the dryer, and put it back on the sofa!
I'd think about using a fine sweater wash in the washer.
Nothing harsh. Not WOOLITE either.
Cascade 220 Superwash wool is on sale at WEBS