1. That is a hard question to gauge. I agree that you could use another SP, but I'm honestly not sure where his value lies right now. My feeling is to start high and work you way down if need be (but not too low, of course). See who needs a 3B, and target those teams...my gut feeling is that you could probably net a guy like Shields, Vazquez or maybe even Cain at this point. Again, it all depends on the league and the needs of the teams, but that is what I'd be looking for.
2. I don't see the need to make these trades. I'd hold onto Broxton since in most leagues saves are hard to come by and if you do make a trade giving one it is usually because a team is desperate and you can make them overpay. If I was completely sold on Valverde, I might go for that one, but I'm not.