In question to the fourth death, in the first part in the live episode a fireman or policeman said about a death in a car from the explosion - unless I heard wrong?
You're right, an unnamed car-driver died in the explosion, not a Coro character as far as I'm aware. Given that this week has been dubbed as "Four Funerals And A Wedding", I doubt they'd show a funeral of somebody who is not a character in the show (unless Roy Hudd begs them to!)
Of the characters: Ashley, Molly and Charlotte are dead-- so three. I suspect Sunita might die, she didn't feature at all in Friday's episode; the attention was on Rita's, Hope's and Peter's will-they-won't-they survivals-- so Sunita's death would be a surprise turn. She did suffer serious injuries as I recall? Also Dev is being written out, so it would make sense.
Back to live episode (a big well done all round), I think a scene may have been missed out. Where did John get that lanyard from and how-- and whom was he impersonating when he 'found' Charlotte in the rubble? A doctor I presume...?