That’s a big bed, your going to struggle to reach the plants at the back if you need to check them for anything, unless your 8ft tall of course lol. I just saw the little trap door at the back can you get in there?
Maybe I should leave my freeze dried coconut water to soak as well. it just seems to float around on the surface, its very hydrophobic, once you get your cover crop going, you wont need much mulch, other than the leaves you pull off your plants when trimming, but you can put some straw down in the mean time and the cover crop will grow through it. It will look great when its all green and lush in there.
You can put worms in your bed as well, I have them in my 10 gal pots.
As Badger said there is a peak time to use tea, 24 - 48 hours after starting, depending on water temps for mine, once it goes anaerobic and stinky its no good, so only make up what you can use in one go, 60 liters is a big load of tea lol.