1. You need to modify event2.
Create a new event, System - Trigger once while true.
Add the Collision event/condition (between player and monster) to it, as well as you add 1 to score.
It now works.
Unfortunately, you can't add the "Trigger once" as "Add another condition", that's why you have to create a new event. But this will correct your "bug".
2. The problem comes from the fade behavior.
I don't master it, but instead of making msg_needmore visible, set its opacity to 100.
Here you go, the msg_more appears again. But the fade behavior does not retrigger. (so the second time, msg_more just stays up, and does not fade again)
I guess you could handle the fading in events. (msg_needmore.opacity = msg_needmore.opacity - 1 until it's 0)
3. Once again, the fade behavior seems making trouble.
I removed it from msg_goodjob.
I also modified event4 so that it is only "System.Score is greater or equal 5".
Once my score reaches 5, msg_goodjob displays.
I guess previously the fade behavior, already had it disappeared and so, setting it to visible didn't work as its opacity was 0 anyway.
So same as 2. you should handle fading in events.
Hope it helps. Nice gfx in your project ;)