Please share with us your general location (or your mom's) so we can get another tech to help you.
The risk to a young child who forward-faces too early has nothing to do with the strength of his skull. It is his neck and its ability to withstand the pressure of the crash. In a FF seat, the entire body is snug in the seat, except the child's head, so the head flops forward. This link below will explain the type of injury that can result from this accident. This child survived and recovered well, but it is a first hand account of what can happen.
http://www.joelsjourney.org/
It is *possible* this seat doesn't work in this card. But, it is almost impossible that no rear facing seat will work. Also, if the tether is your biggest concern, there are rear-facing seats that can be used with a tether - the Sunshine Kids Radian, most of the Britax lineup, and then there is the True Fit Premier that has an anti-rebound bar.
I am going to hunt around this site to find other references to this vehicle to see what people have had luck with RF.
Thanks for being patient and advocating the safest way to travel for your child. Kudos to grandma and grandpa for being so flexible too.
Most of us would opt in a hearbeat to use an untethered rear-facing seat for a child this age rather than a tethered, forward facing seat.
