I share a bottle of wine with my MiL every Saturday, that is the reason why I use my syns on a weekly basis, could you save the syns for tonight?
I also have a smaller glass for my wine, I've measured it & it's 150mls, I only fill my glass when it's empty & that's how I keep track of what I'm drinking. I don't think half a bottle of wine is unreasonable or excessive.
Sainsbury's do a non alcoholic beer Chec (crickey can't remember how it's spelt now) its a 500ml bottle & only 1 syn.