Fair value that a risk averse individual would pay to enter a gamble
Yes.
In general not.


Let's say the individual has initial wealth $W$ and the gamble $g$ has payouts $0$ and $G$, each with probability $1/2$. As you say, the certainty equivalent $C$ of the gamble is the amount $C$ with $$u(W+C)=(u(W)+u(W+G))/2.$$ Now the same individual would be willing to pay at most $P$ to enter the gamble, where $$u(W)=(u(W-P)+u(W+G-P))/2.$$ So if $C$ is the certainty equivalent of $g$ at wealth level $W$, then $P$ is the certainty equivalent of $g$ at wealth level $W-P$. If $u$ is linear, then $P=C=G/2$ follows, but in general $C$ will differ from $P$.