Updated my Pinterest with the fit pic seen here:
At the waist, I think the 30 will be fine. I wear 30s in N&F weird guy, and 31slim in Gustin - pretty similar fit. Regarding the big thighs, if the weird guys fit okay in 29, I don't see why 30s wouldn't work for you. If the weird guys are tight in the thighs then may be go for the 31s. Best bet though is to measure and check against their fit guide - I think it's pretty spot on.
These aren't my posts, but each links to some pics of #77.