Do you mind if I drop you an email to exchange some ideas?
Your Kepler's equation solver looks like a pretty standard textbook Newton iteration. I'm sure you're aware of its shortcomings, look at libtwobody for a more advanced solver (Laguerre-Conway) and the bibliography for the papers describing it. There's also a universal variable solver which doesn't have issues for near-parabolic orbits and handles elliptic/parabolic/hyperbolic orbits with no special cases.
I've also got an interest in 3-body and n-body stuff but so far I've concentrated on the two body mechanics and dabbled a bit with simulating rocket launches.
Your Unity Asset looks pretty interesting. Has it been popular? I've also considered making (code) assets for Unity, so please do share any experiences you've got.