Regularity Hodge Laplacian on bounded domains

Question

I need a reference for the $W^{s,p}$ regularity of the Hodge boundary value problem on bounded domains. I need estimates
$\lVert \omega \rVert_{W^{s+2,p}} \leq c \lVert f \rVert _{W^{s,p}}$, for $s \geq 0$ for the system,
$\Delta \omega = f $ in $\Omega$,
$\nu\wedge \omega = 0 $ on $\partial\Omega$,
$\nu \wedge \delta\omega = 0 $ on $ \partial \Omega$.

I need to know,

1. A reference which actually verifies the Agmon-Douglis-Nirenberg condition for this system for general boundary.... most references either do not verify or verifies the condition only when $\partial\Omega$ is flat.
2. I need to know whether regularity results extend to the scale of negative Sobolev spaces, i.e.,
   if $\lVert \omega \rVert_{W^{1,p}} \leq c \lVert f \rVert_{W^{-1,p}}$ is true?
3. Whether there is such a result for the system
   $\delta ( A d\omega) + d\delta\omega= 0 $ in $\Omega$,
   $\nu\wedge \omega = 0 $ on $\partial\Omega$,
   $\nu \wedge \delta\omega = 0 $ on $ \partial \Omega$.
   where $A$ is elliptic?