1. How old is the tablet?
2. Exactly how many apps do you have running in the background?
3. How many of these apps are fetching data/trying to fetch data?
4. Why are you running it on safe mode?
5. Are you somewhere with strong Wi-Fi signal?
I think your culprits here are weak WiFi and probably a number of apps fetching a lot of data in the background. If you have apps that give you a lot of push notifications, then your tablet is constantly pinging these services back and forth checking, which inevitably causes your battery to drain. Though the screen usually chugs the battery the fastest, a lot of apps in the background fetching data will drain it as well.
When you check your battery options, what does it say is eating up your battery, what apps?