The thing with Yanmega, however, is it's a lead for a reason. Stealth rocks do 50% damage to his HP.
If you want Hydro Pump in Salamence, you breed a male with the desired move who belongs in the same egg group as Salamence and his evolutionary line.
In this case you'd breed a male Gyarados that knows Hydro Pump with a female Bagon/Shieldon/Salamence and the baby Bagon will know Hydro Pump.
Yes, the Skarmory is still EV trainable.
On Infernape/Yanmega: The advantage of that Infernape is that Blissey will never survive a Close Combat. Yanmega obviosly has his coverage advantages though. STAB Bug Buzz is a killer, and Air hax Slash will kill fighting types as well as other buggs not named Foretress and Scizor.
On Kingdra: Yes, IV breeding, but I assume you don't know how to do that. If need be, I can breed the pokes, but I can't EV train anything untill I finish Diamond (just beat Wake). I have several Kingdra spreads that I myself want to do so that'll be fine.