Ixixly
What sort of vehicle are you driving?
From your info, you couldn't have picked more expensive fuel stops if you tried.
Barkly Roadhouse and Three Ways and Dunmarra are all expensive. Tenant Ck is 10 to 20 c/litre cheaper than Three Ways, but 25km each way from/to Three Ways.
Cloncurry, Isa, Tenant Ck, Katherine.
The route you've shown from Dunmarra to Kununurra is best tackled in a 4wd.