Whats a tidal leash? The same thing as a tide?

I agree with what you said: The Poisson brackets as Lie-brackets should generate curves (orbits) on your manifold. And since H commutes with the constrain, H stays invariant in this curve

I get your point. What you are saying is that including backreactions on the source makes the maxwell field equations non-linear. But I would define additivity not in terms of variant sources, but rather fixed. And then the additivity comes solely from the linearity of the equations in the force. This is not the case for GR, which even in the absence of backreactions are non-linear.

I admit I should have worded my answer from a different perspective: Einstein gravity has a Levi Cevita connection which in turn is NON LINEAR in the metric. And the resulting geodesic equation thus does not depend linearly on two fields, and effectively means what I then stated at the end: One cannot add two fields together. This is in contrast to Maxwell equations, which are all linear, and so actually fields are additive.

But that is because your fields actually change the source strength! The point is, that given the charge distribution (including the dipoles), the forces (electric fields) are additive. The fact that taking away some of the sources results in the other sources changing is not the point of the discussion.

@GiorgioP-DoomsdayClockIsAt-90 Then what does? Or rather, why does the second law not imply the additivity of forces? Can you explain?

Was the "I do not have an answer" in the sense of philosophically that it is unclear why the universe should be stable or is the Ostrogradsky instability unknown to you or am I just missing something entirely?

A nicer answer would be better, but just so you know: Even if the electron is not how you describe it, it will still interact with itself. So depending on what exactly you expect, the answer is either trivially yes, or something "different" (i.e. the interaction behaves like two electrons, but this still is hard to differentiate between just one elrctron).

It is hard to define a rest frame for particles that go beyond the speed of light. Unless you accept that causality is wrong and or your metric changes completely (including being completely 0)

I dont get why doubling the mass doubles the angular acceleration

$q$ and $p$ are not independent if you just plug it back into the lagrangian, as seen by your equation for $p$.

@BowlOfRed So what about physics? What do physicists mean by condensate? Not the colloquial usage of condensate.