Oh gosh, I have no idea. Like you, it's hard to know because all babies are different. I think you know best, if you think something else is bothering him, it probably is.

So I will just answer your questions based on what my babies did if that helps??

So, is it normal for a 5-6 week old not to sleep/settle between feeds?
Around this age mine went through a period of being more wakeful and harder to get to sleep and some days I just couldn't get them to sleep for hours. It was just a wonder week and it passed.

To keep spitting up/vomitting up to 2 hrs after last feed?
Mine sometimes did. I didn't have real spewy babies. They would chuck up a little after most feeds, sometimes a lot.

To feed every 2-2.5 hrs during the day?
Very normal.

To feed 3 times over night?
Yep, both mine fed at least this much and then when they got a bit bigger even more *sigh*

To cry for 1.5 hrs during/after some feeds?
Not for my babies no, they really only cried because they were tired and sometimes after a feed if they had an upset tummy but not for that long.

To vomit up to 6-8 times after every feed?
No, mine didn't this much so not sure on this.

To wake suddenly from sleep with crying out, even after only being alseep for a few minutes?
Yep, especially if I had held them to sleep and then put them down.