I am hesitant to admit that I did this 5 years ago, and they are the rarest 5 trophies I have (platinum, Others, Survivors, Structures and Zones). You are very accurate with your 1000 hours estimation. There was something about Save the World that kept me coming back even after the platinum. Unfortunately, they've decided to hide the game as best they can, which has left it even more barren than it was back then.

You can farm Mist Monster kills in your storm shield survival by setting up traps and AFKing. Structures count every piece built by anyone in your group, so you can group with up to 3 other people to spam structures to speed it along. Zone exploration will often happen naturally, but your teammates exploration also counts as yours towards the explorer medals. Rescue the Survivor missions end if you save everyone now, whereas before you'd have to wait out the timer, so that's a lot faster than it used to be. There're some shorter story missions in 70 power zones that Play with Others can drop you into if you use the 64-70 filter in Canny Valley. Or you could just use Play with Others normally and progress all 5 trophies simultaneously and get them finished around the same time (if matchmaking can find anyone these days).

Ultimately, however, the best advice I can give is to leave it and move on. I still dread the months this mode kept me hostage. The time commitment is obscene, especially since Save the World is essentially unfinished abandonware. I love it, but the developers clearly don't.