Page 121 of the book states a character with 20 or less Corruption Points can benefit from the Simulacrum Imperialis to roll a d10 to reclaim a spent Fate Point (succeeding on a 8, 9 or 10). Void Born gain a power that lets them reclaim any Fate Points they spend only on a 9... does this mean a Void Born gets two chances to declare his Fate Point unspent, or is it one d10 roll against both his power and that of the Simulacrum

I dont think so. I would say its either one or the other. Or you could say that being void born increases that chance. So he would reclaim lost FP from 7 up.

For a similar effect check page 106, "Grace."

"If the faithful is a Voidborn, this roll replaces the roll from the Charmed Trait."