According to my second question, I think that a possible answer is to check the number of non-vanishing components of the regarded connection. In the case of the spin connection and the Schwarzschild space-time, there are four non-vanishing components and therefore it cannot describe the SO(3)...
In the framework of Einstein-Yang-Mills (EYM) theory, suppose the following action:
\begin{equation}S=\int\left({\kappa R + \alpha tr(F_{\mu \nu}F^{\mu \nu})d^4 x}\right)\,,\end{equation}
where F is the gauge curvature associated with a non-abelian Lie group G and a gauge connection A. Then...