I agree weight limits are often understated but probably not by over 150 lbs (bike plus rider). Sometimes the minimums are caused by lightweight rims, particularly those with under 40 spokes. One option is to find a fat tire bike without suspension and swap the rims if necessary for ones with double walls and at least 36 spokes, ideally 40 spokes. Also, don't be concerned about the seat which is an easy and inexpensive change.