I have 2 questions regarding the ADV3219 mux:
Apology for the very late reply. To answer your questions:
1. The worst case BW that you may get for a 4.5Vp-p is ~156MHz. I computed this using the formula of f=SR/(2*pi*Vout).
2. Yes you can do this but I think the better way to do this is by using a 4:1 mux like the ADV3221.