3) To me it's 99% Eugene or Abraham that were killed. From a show perspective, you can remove Daryl. Too popular and allows them to stray from the comic because he isn't / wasn't a character. It can't be Rick (as leader), or Carl, as his son (although that would help with his aging problem). Glenn is a possibility (especially considering this season's tease of his death), but if Negan knows Maggie is pregnant, that might push the Alexandrians too far.
They blatantly set-up for a loss of Eugene (I'm a survivor, here are my plans Rick), and Abraham (can we have lives like Glenn and Maggie). Plus their goodbye embrace. If I'm Negan it would be Abraham. Take out the guy that looks bad-arse and not scared. Leave the weak one behind (Eugene) that will probably not instigate future problems. Also, the group was willing to sacrifice Eugene (leaving him with RV). Don't let them dictate who I take out. The reason that it could be Eugene if I'm Negan? Eugene might not be too important to making the stuff I need. Also, how does Negan recruit all these tough, depraved, psychopaths? Abraham certainly has a look like he could be one of them.
I'm going with Abraham. Next season we'll pick up in a beaten-down Alexandria that is subservient to the Saviors. We'll find out who was killed when Glenn comes in and asks Maggie "how is Baby Herschel Abraham is doing." The rest of the season will be about back channeling between Savior subservients. Carol and Morgan will try to convince Don Quixote and his group that the Alexandrians can be trusted. Eugene will either: 1) secretly build their bullet factory which will eventually be distributed to the subservients; or 2) the bullet factory will become what Alexandria can produce for the Saviors.