Given a set of LTL formulas, on which states does the Kripke structure hold?
A couple of comments:


Note that "in the future" is not strict, i.e. $Fb$ is also satisfied whenever $b$ itself holds.
Looks fine to me.
Also ok, though I'm not sure if your interpretation would be very enlightening in a more complicated Kripke structure.
"$Xa\Rightarrow Xb$ is true for every state" is a CTL-ism. What you want to say is that for every state along every path, if $a$ holds in this state and $b$ holds in the next state, then $a$ also holds in the next state.Is this the case?
Here you want some finite number (possibly $0$) of $a$s, followed by some finite number (possibly $0$) of $b$s, followed by a $c$. Is this what you see along every path starting in the states you give?