Front V Brake squealing on Trek FX 7.4
Since a single pair of V brakes is not much more than 2-3x the price of decent set of pads, why won't you try a different pair of V brakes? It's not hard to install, only bit more work as changing the pads. Also having some play on the brake arms is a cause for concern -- there shouldn't be any play in decent brakes apart from sidewards play against the spring due to the pad gap.
In one of my bikes, the front brake squealed like hell. It's not V brake but cantilever. I assume some combination of cantilever brake arms, rims, fork and pads caused the squeal. Changing the Kool Stop salmon pads to Shimano S70C pads fixed the squeal for me.