Hey there,
Know that various amps, consoles, active DIs etc have different input sensitivity, so it will vary for whatever you're plugging into. Also that the T5 is wholly different animal so apples/oranges there. And and yes the ES2 is a bit of a low signal so the input gain (like on a mixer) does have to get a bit hot. That said, it is still well within the range of "no issues." Verify that all three knobs are at their detent, 12:00.
1. Since you already have the .050" allen wrench, loosen them and be certain your saddle is sitting flush into its slot. With the piezos loose, you can pull the saddle out easily without effort. So when you set it back in, just be certain it's sitting in there squarely.
2. Now tighten each allen screw "just a bit" so there is slight bit of tension, not more, just a little is all. With all three situated thus, your saddle should be held in by the piezos and not drop free out of its slot.
3. Now plug in and adjust each piezo tension screw. Preferred is if you can listen through headphones as you can discern much more clearly the volume difference as you tighten/loosen each screw (which adjusts pairs of strings, naturally). If you're not setup for headphones, then plug in and set your amp's volume reasonably high and hear it from across the room (only so you don't feedback under the volume) as you're trying to hear the pickup and
not the guitar's top. Adjust the screws to get your max volume. Caution: too tight and you'll get not just volume but a harsh, brittle timbre at the top end. You'll hear it, which is your cue to back off the screw a hair.
If this doesn't give you enough gain for your Loudbox then you may have a legit issue with your preamp. Chime back in with waht you learn.

Edward