If I understand your project correctly, I think you need something other than a dpdt relay ... the seat switches are not rocker switches, they're actually momentary contact 3-position switches, with the unloaded position being "off". A DPDT relay would always be either in the "seat moves up" position or the "seat moves down down" position, never in the "seat is adjusted and not moving" position.
Or I misunderstood ... in which case, never mind!
