How would I calculate the DC Gain for a Chebyshev Type 2 filter?
I suppose that you obtain a transfer function of the desired discrete-time system in the form

$$H(z)=\frac{b_0+b_1z^{-1}+\ldots +b_Nz^{-N}}{1+a_1z^{-1}+\ldots +a_Nz^{-N}}\tag{1}$$

From that transfer function you compute the coefficients of the second-order sections. Before doing that, you can make sure that the DC gain of $(1)$ equals $1$ (which of course only makes sense for a low pass or a band stop filter).

The DC gain of $(1)$ simply equals

$$H(1)=\frac{b_0+b_1+\ldots +b_N}{1+a_1+\dots +a_N}$$

Obviously, the DC gain is independent of the chosen filter type.