Yes, if it's fated, then it's not free will. See why I loathe fate so much. If no choice can be truly made then what is the point? I don't believe fate determines choice at all because than it's not a choice. It's just meant to happen.
I mean the original lifespan is seen. In the case of Rem, since taking the eye deal requires half of the lifespan to be cut in payment...it could cut the numbers in half that are seen since the payment for the eyes is half of the remaining lifespan.
Actually, suicide isn't a special circumstance. The rule merely states suicide can be used as a manner of death because it isn't thought to be out of the realm of possibility for a human to commit it. If it would be, then the heart attack default death woudl kick in.
It might not be impossible, but it isn't logical. For Misa to only live 6 years...and those years came from L, Watari, and the person Rem killed in the car...Rem had to be almost out of life when she killed L. Rem, who wanted to stay by Misa's side and make sure Misa lived a happy life...wouldn't make sure she had enough life to see it? Rem would have allowed her own lifespan to fall so far behind Misa's that...knowing Light had already threatened Misa's life and most likely would kill Misa to further his own plans, that she would allow herself to die because she didn't make sure she had enough life? Rem only died because Light arranged it so. Rem didn't actually intend to die.
This is assuming Ryuk knew enough about the notebook to come to that conclusion. Ryuk admits he didn't know much about the Death Note and when Rem mentioned a rule, Ryuk openly admitted that he didn't know that. Ryuk isn't the best source of information. Plus, Light's lifespan probably wasn't accurate to begin with. Using a Death Note can either lengthen or shorten the person's life, but again only the original lifespan can be seen. I know it says that in the rules many times.
You seem to be basing all this on fate determining the lifespans. I view it more as chance. Everyone born does die...it's just a luck of the draw when.
Did you ever look at a picture of yourself and see a stranger in the background? Makes you wonder how many strangers have a picture of you.