While it's obvious the Son'a weren't entirely upfront with the Feds, I don't think there's any hard evidence indicating that they wouldn't have gone through with the deal.
I'm not sure what you're talking about with regards to committing suicide. The Son'a and Feds were probably going to split the particles evenly between them.
exactly. Using the "Son'a were going to betray them" or a "the process wouldn't have worked anyway" argument are both ways of avoiding the actual issues in the film by substituting arguments for which there is no evidence.
Again, the Son'a were NOT Dominion allies, they were merely selling them drugs, just as I'm sure they'd have been happy to sell weapons to the Federation. They only became Dominion allies after Picard betrayed the agreement and fought against them, at which point, why WOULDN'T they have become Dominion allies?