That won't work. While the Ears has an envelope follower, it and the rest of the module is designed around the contact microphone built into the module itself, so that the module works as a 'tappable' controller. You're trying to use a proper microphone setup on a drum kit instead. What you actually need is a proper external input module with a mic preamp and envelope follower...or better yet, a multichannel input module and some separate envelope follower modules. But as an indication of what's required to do this, have a look at a Doepfer A-119; this module is sort of the standard for the group, with a balanced/unbalanced input preamp with the proper impedance for external sources, envelope follower, audio output at synth levels, and a comparator to set a level for a gate. That's what needs to be used.
As for the MPC...why not just use it as a proper MIDI controller/sequencer, instead of a more difficult, roundabout and potentially glitchy (not in a good way) method such as audio triggering? Notice, also, that the Ladik module has only one adjustment for its comparator level to generate triggers as a desired audio level. Really, what the Ladik module is better designed for is for use with drum trigger pickups...which are basically insensitive microphones designed to be drum-mounted so that when the drum is struck, it outputs an audio signal (albeit not a very good one) that can be converted by circuits like the ones in that Ladik module. This isn't the right use for either the MPC or the Ladik module; just get a MIDI-to-trigger interface and connect the MPC to that directly via the MPC's MIDI OUT.
Anyway, those need fixing first. There's other problems in this build, but you need to correct the premise behind it first.