1. Aerodactyl and Metagross are really the only two. I'll give you that one anyways since they're pretty common (even though Rotom-A fixes the Metagross Problem).
Azelf speed ties, so 50% chance there. Forretress is getting its rocks/spikes either way, Skarm is coming in and spiking, etc. Heatran gets rocks down for free as well. The only suicide lead this concretely stops is Infernape, and beating one lead does not count as "stopping rocks" in the long term.
2. I'm saying this from experience: They do not switch. Nobody in OU is threatened by an Ambipom, especially Machamp. The only thing I can say is try it for yourself and you'll see.
Don't say your set works because people are bad. People that let this happen are playing Machamp wrong anyway for the most part, and the fact that this Ambipom can score a surprise kill with its gimmick move does not make it a superstar. Same with people that leave Swampert in on this. The fact that they're ignorant of Ambipom potentially packing Seed Bomb does not make Ambipom good.
3. Dead weight? He is far from it after he takes out leads. Fake Out can easily pick off any non-Steel/Rock type (deals 38-45% on Salamence alone). He's also incredibly fast and can come in to take out Infernape who are in the middle of a sweep. Dead weight is a Swampert after a Seed Bomb or Gengar after an Aerial Ace. Just because he's not packing Double Hit or Return doesn't automatically mean he can't do anything.
As I said before, I'm not about to praise a set that allows my opponents to waltz in with Heatran, Jirachi, Skarmory, Forretress, Rotom-A, Scizor, Gyarados, Lucario, etc. and get free turns on me. Too many liabilities midgame for me to even consider putting this on my team, lead or otherwise.
To those that say that you can just throw on Tyranitar and Magnezone, that doesn't even consider the fact that 1: I'm building 1/2 of my team around compensating for my lead's mediocre type coverage and 2: I'm still dealing with other key Pokemon being huge, huge pricks to me at any given time.