Based on your photo of your rear tyre @Cuppa I reckon the Nitto that Winnie pictured might be the go. The dirt roads are brutal. A muddie will disintegrate i reckon.

I spent 2 years in Northern PNG in the early 1990s and was killing 4 sets of tyres a year. Rubbish 3rd World tyres im sure but they just disappeared.

They are harsh conditions for a rubber tyre. You are heavy. A heavy tyre means more body. Go heavy I reckon.