Schwalbe has a Marathon "family" of tires, Continental has a Contact "family"; consider the Continental ?
My mASS i similar to yours and I've carried 10-20 kg of stuff on a Surly CrossCheck with 42 mm regular Schwalbe Marathons on road conditions like you indicate. Including broken pavement, limestone gravel dust, muddy & rooted paths, regular gravel roads, etc- have had great luck with this tire.
ps - also look at Schwalbe's Hurricane - if you are needing a little more traction.