Re your answer:
Statement 1 follows from Weyl's inequalities and $\rho_1(C) = O(\lambda^{-1})$.
$2 \implies 3$ seems problematic; what if $\rho_i(M)=0$ for $i>1$$C = \frac{1}{\lambda^3}I$, which is perfectlyshould be possible given the definition of big-O? For instance, $C = \frac{1}{\lambda^3}I $ should giveThen $\rho_1(M^{-1}) \sim \lambda^2 \not\in O(\lambda)$.
Statement 4 seems just the matrix norm inequality $\|M^{-1}e\| \leq \|M^{-1}\|\|e\|$.