Okay, here's my two cents:
Yes, adamentium is "indestructable". Think about it though. They said that adementium scratches adamentium, right? So wouldn't adamentium ENERGY blow up adamentium? Isn't Gambit's power the ability to tap into the potential energy of an object and use that to turn it into an explosive? That's my opinion anyway.
No, no, no, Gambit is faster, one of his mutations is that he is much more agile than others, Wolverine is fast, stronger I'm sure but he is also slowed down because wouldn't you think a metal skeleton would weigh a bit? It's very close. When Gambit had his original powers (before the operation by Sinister and again when he came back from time travel) he could kill anyone, from a distance, even charging living things with the kenetic energy. Without his original powers he probably could charge Wolverines adamantium but I can't envision a situation where there would be an opportunity. Wolverine would probably kill Gambit before he could try that, but the fully charged Gambit with his natural born powers could take Wolverine in seconds.