All those rates except Rest of the World charge a flat $5 extra for the first item, which is easily enough accomplished with a $5 Handling fee (which only gets added once to each order). Then you could just set up the rate for each add'l item with a "Price per unit" rule for each country. The first unit would add the Handling fee plus the per-unit fee to the buyer's shipping charges, then each add'l item would just add the per-unit fee.
That Rest of the World (RotW) rate is the tricky one here, with an $8 difference between the first item and each add'l item. If you could consider charging $15 per unit for RotW, that plus the $5 Handling fee would cover your $20 first item shipping cost, but then each add'l item would wind up overcharging by $3/unit. If you expect to get more multi-unit orders than single-item orders for RotW destinations, you could consider charging only $14 or $13 per unit; then you'd only lose a buck or two on shipping for single-item orders, but you'd make up that difference on multi-item orders.
Note that you can restrict which countries you will ship to, in your Shipping Destinations list. Then you can create a rule for All Countries that would cover every selected Shipping Destination country that doesn't have a rule of its own. You'd want to use an All Countries rule for whichever rate class covers the most of your Shipping Destination countries, then you'd just need to set up a rule for each country that doesn't use that rate.
