with a more than half of tank of gas and the gas pedal to the floor my car misfires and sputters

what does a 1/2 tank got to do with that,other than load,therefor,ide suspect spark area like coil,wires,and that little black sensor on firewall with a vacuume hose on it

Sounds like what my Regency Brougham did w/ vacuum leak

Could be a vacuum leak but it could also be a burnt gas pump. If your vehicle is taking up more gas then it should be, or your smelling gasoline when exiting the vehicle, that's a sure sign that your gas pump is gone. They're not extremely pricey but they're not cheap either, typical cost would be around $80.00 to $230 depending on what the shop charges and parts. Check the hoses, it could just be a bad / rotten hose.