Good question, Paul!
i know what is "normal" for me - that is - how i usually react to triggers or memories or the painful feelings that come up - sounds like that is what you are describing. that is not necessarily the way others respond - but i think there is enough commonality that we can all relate.
what you have described very well is the way i used to feel too. then for a while it was less ups and downs and more like a constant deep pit. BUT now i am at a stage where the "troughs" are not as low and don't last as long. and some of the highs are higher. last week i realized at one point that i was feeling as calm and relaxed and good as i only used to feel after having a couple drinks. and i hadn't had a thing to drink - honest! that was a great feeling!
so - yeah - if there is any way that "normal" can be used in this context - i think that you are right on. maybe a better term would be "typical" or "predictable." bottom line - it can/does get better with time and work. (and i gotta say - my version of "normal" changes as i learn to deal with and overcome all the bad stuff!)
hang in there... you'll make it!
"Tell your heart that the fear of suffering is worse than the suffering itself... And that no heart has ever suffered when it goes in search of its dreams, because every second of the search is a second's encounter with God and with eternity." - Paulo Coelho