[Attempt #2...god, I love what accidental keystrokes can do in Windows. Feh.]
OK...some things were removed, notably the Audio Interface. It doesn't work like you think it does. It's just an analog stereo out (which you have already) and a stereo in (for which you don't have the space in this to process incoming audio). I also took out the effect insert module; again, it's not going to be that useful, plus I added some effects (notably a Juno 106 chorus clone) to better suit this build.
I shifted things into their respective signal paths, also. The 'monosynth' is up top, 'drum machine' is down so you can easily access the sequencer like a playing surface and get at the knobs for on-the-fly tweaking.
As for the 'monosynth', there's now two VCOs. Running just one often results in a thinner sound, but with two, you can do some slight detuning and generate that big, harmonic-sweeping sound for heavy bass. One can also sync with the other for weird lead timbres, too. I set up the modulation section so that the Disting is in position for multiple usages, and Maths provides control curves for the two VCAs, through which you can feed two different waveforms from the LFO. By doing that, you can cause things like delayed LFOs, LFOs that rise in amplitude over time, etc. Added a pair of AR envelopes for the VCF and its internal VCA...that module is a Moog Rogue VCF/VCA clone of sorts. I went with that because it's going to be a bit dirtier, which will punch the monosynth signal out better.
'Drum machine' is the Circadian Rhythms, then there's a passive mult to allow you to distribute a pair of triggers to other points in the build. Drum modules are an 808 and 909 kick (more BOOOOOM), a Delptronics module + expander which has some 606 and 808 characteristics, 909 clap, 808 maraca, and 909 hats and cymbals.
After that, there's a submix for six of the drum modules. Yes, there's more than six, I know...but certain ones you can run through this stereo submixer, then mash via the MSCL stereo comp/limiter and pound the HELL out of the sound that way, while still sending a couple of other drums, plus the monosynth's VCA output, through the main mixer up top. The 106 Chorus can then either be used as an inline effect for the monosynth or a mono drum voice before mixing that into the other stereo input on the main mixer. The first stereo in, of course, is where you'll want the drum submix (and MSCL, if desired) fed.
Yes, the main mixer is possibly overspecced on inputs. Trust me, you want that. Anyway, just feed the stereo out from it to the Output, take your headphone feed and stereo line-outs from that, and that should do it.
It's a relatively simple build, mainly owing to space constraints. And frankly, before going all the way in on this (especially the drum part), you might want to take mixxalot's advice and look into some more prebuilt gear. I would suggest checking out the Roland TR-8S (the new one, not the original TR-8) for drums; by doing that instead of going with much of what's on the bottom row, you then open up a LOT of options for the modular which, with the Circadian Rhythms, you've kind of got 'locked' into a specific usage at present. Besides, the TR-8S samples, has the 808, 909, 606, and a few other Roland kits standard (no 'plug-outs'...ugh), multiple assignable outs, and works like the 909, more or less. And it's about $650-ish over here. There's a couple of other things that come to mind, too, such as the MS-20 Mini + SQ-1...one of Aphex's longtime mainstays. You might also consider losing the CS-1X...it's sort of 'vanilla', doesn't really rip through a mix very well, which is typical for Yamaha's analog modelers. Pads and such are OK with it...but other things do those as well or better, and more besides.