REAR Seatbelt Questions

I only have info on Ohio laws, having said that, there is no Ohio law (or anywhere else here in the states that I know of) that prohibits putting a child seat in the front seat. The cautionary factors are the proximity to the airbag, and that applies to a rear facing infant seat. STATISTICALLY, the 2nd row, middle seat in the safest, but if you look at it from a common sense stand-point, it is because that location has the most metal around it.
As far as adding belts, I would not recommend that, reason being, and only in the most severe cases, that car is designed to "Fold" or callapse in pre-determined specified ways. If you anchor a belt to point that may push out, you are likely to do more harm than good, especially in the full booster-type seats that use the exisiting belt to hold the child and not just the seat.
FWIW I would say find a seat compatible with just a lap belt and stick to the back seat, anything else could pose unforeseen ramifications. -Dustin