Do the new nets fit in a tackle box? Really really really good question. No idea, since I don't own a tackle box. Can anyone enlighten? They can be added. I tried it right when I got them.
You could loot the shipwrecks for low-medium loot. Best things I saw were adamantite ore and cut rubies. You could also only loot 3 items in total. If you haven't done the 10 extra hunts, you can loot the shipwrecks there.
If you're having trouble with that trophy, here's what I did. I played games with random people until I found one who had to do the calibration course. Once the game started, I added him on Steam and left. Then (after waiting for him to accept me), I invited him to a new game and bingo. In other words: you have to be friends before the game starts. It might take a while though, since people are still people.
Looking at how they're doing at the moment, I wouldn't be surprised if it took that long. Still, they're going to bring several functions back over the course of time, so we'll probably have online play back soon-ish.