That's an awful lot to take in in just a month or two. Surprised you can list all that off like that! Pretty cool.
Must have been kind of wild to get all that information in such a short time. It took 10 years for a lot of us and there were a lot of mysteries and theories.
I assume youve only played the games and not gotten into the books or comics yet. Did you feel like 4 had enough context for its events to still make sense? Did it leave you confused about anything?
How about what you've played of 5 so far? Same question.
Before touching Halo 4, I had watched all the previous games' terminals (including reading the Halo 3 terminals) so I wasn't completely lost. When I saw the Didact, I didn't say "Who?". I was more like "Holy crap, so that's the Didact?"
Admittedly he's barely referenced in previous games. In Halo 1 or 2 there are terminals where 343 Guilty Spark refers to the Didact + Librarian and Halo 3 terminals have lengthy written conversation logs between the Didact and the Librarian. These characters have small nuggets of information hidden throughout the previous games but they're there nonetheless.
So by the time I started Halo 4, I knew the Didact and Librarian were Promethean and Forerunner, I knew they were responsible for building the Halo array, I knew the Librarian was level-headed and the Didact had a bad temper, and I knew the Librarian was dead.
Having said that Neogaffer Barrow Roll recommended I watch the Halo 4 terminals as I play the game - initially I ignored his advice but I'm very glad I relented. It helped make his motivations (i.e. Why is he angry? What is the Mantle?) much clearer.
Re: Halo 5 so far I love it. The game is gorgeous, fun, performs excellently, has a great art style, interesting story, good level design and gun play, and great characters. Love Lasky, Locke, Palmer, Buck, Chief, Cortana, Halsey, etc...
Am I lost? No but only because so much is fresh in my mind. I know exactly who Buck is thanks to ODST. I know about Jul, Halsey, Lasky, and Palmer thanks to Spartan Ops cutscenes (which are part of Halo 4). This is all without me ever having watched a movie, seen a show, read a comic or read a book.
Locke, Tanaka, Vale, and Blue Team are all new but I'm managing. From playing Halo 5, Locke is clearly a top-tier ONI spy/agent/spartan, Vale is awesome because she can speak Sangheli, and within a couple of missions it's obvious Blue Team are tight-knit like a family. Blue Team probably could have used more back story... That was a missed opportunity, but I'm gleaning enough information off the cutscenes to "get" what Blue Team is all about.
After starting Halo 5 I've watched the Forward Unto Dawn movie and episode 1 of The Fall Of Reach show. I enjoyed them both.