Not sure what a lot of your units are, but the gas constant has units of J/k mol (typically). This gives Ea/R units of temperature because Ea has units equivalent to, say, J/mol. So if the slope is equal to 9172.8 K, and R = 8.3145 J/mol K, this means Ea is equal to 9172.8*8.3145 = 76503 J/mol, or 76.27 kJ/mol. Not far from the Ea listed. What am I missing?