ok, so, can you tell me at least what the physical dimensions are, like how long and tall the ship is. If the ship is lets say, 20 inches or so, I would say .40mm for standing rigging which includes all the stays, and shrouds. Then roughly .12 mm or even .09 mm for all the running rigging. (Yard Lifts, Sails management, Yard Braces)
For a ship that is 1/90 then you will need .80 mm .20mm and .12mm
But it seems as if you are probably working on something smaller. If you have like a Hobby Lobby close to you, I know that they have several dimensions of nylon you can use. If not, then you might can get by with using cross stitch thread and 'separate' the thread into the size(s) you need.
Get a good high quality bees wax and run the line through it several times so that the rigging line will not have any fuzzies.
Concluding, you need to get a dark brown or black for the heavy lines and a tan color for the running rigging.
So, your first photo, I assume that you have already taken all the rigging down? I think I still would stick with the .40 or .50 for the Shrouds and Stays if you desire to do that. I would also stick with the .12 for rigging the yards lifts etc. For instance .40 x (.30 percent) = about the difference in size. Which is about .12
.40mm x .30 = .12mm (that is 30%)
.50mm x .30 = .15mm