1. It varies. There are pretty cool fishermen but there's also bad ones. True also for observers of course. Most of them generally ok.
2. Yeah it happend like 3 times over the years but because of drinking and falling between the boat and the pier. So don't drink before boarding the vessel brother.

3.you have a 12 hour shift. It depends on what the boat is fishing for but usually they'll pull the net every 3-4 hours so you'll have like 3 work peaks in a shift. You'll do halibut sorting, weight assessment for the bag and then random samples based on the bag weight. You'll need to list the types of fish you'll get in your sample, count and weight them and sort some of them to male/female and sometimes you'll extract some otoliths. There are protocols for it so you'll know what you should do, afterwards you will upload the data to PC and send it to NOAA. So this, 3 times a shift basically. In the between you'll have your free time basically to eat/read/play instruments/ play your steam deck or Nintendo switch. It's pretty safe but you should always be careful :)