I actually threw it away already, but I’m wondering if maybe I shouldn’t have.
Why not? Alcohol’s a decent method of sterlization.
Probably. Depends on the vodka content, but it should have been okay. Might have tasted a bit stale, or if it was open, it might have taken on foreign flavours from other stuff in the fridge, but no food poisoning for you…
If it smelled okay, and wasn’t fuzzy, it was probably safe to drink. As safe, anyway, as when it was fresh. 
Since I’d have no problem with week old Splash (if a fruit flavor), adding alcohol to the mix would only have extended it’s refrigerator safe life span.
I’d have dumped it, as the ingredients arent expensive enough to warrant not having a “fresh one”
I don’t know, but when I was in high school some genius gave me a fifth-sized bottle of vodka and orange juice, and I hid it in my friend’s bass drum for 5 months, and then we drank it and it was fine.
What?
If you’re referring to Tango, I doubt there was any actual OJ in it.