1. I was thinking more of countries like Liechtenstein, Monaco etc which seem to have actually done quite well considering that they're not on the list above. For example, considering Monaco's overpopulation and likely lack of any viable food source for most of the population, I would not be surprised at a complete collapse and reversion to pre-technological levels.
2. So from your explanation it appears that it is quite possible to have journeys between two planets as long as both have the capability to build a rocket that can reach space, even without a mass driver. If so, it's curious that of the 148 planets with space travel capability (with 57 having mass drivers) only 17 have actually sent manned expeditions to other planets.
3. The first option seems better. Otherwise people in the UK and Togo will be quick to claim that they are best because they're closer to the original.
To be quite honest, I've never believed in true technological regression in post-collapse societies. Stagnation, certainly, but people wouldn't just abandon literacy, education, and technology altogether. Even in post-Roman times, there were technological innovations such as the horse collar, grindstone, and heavy plow.
In any case, small countries get a penalty to technological development in my model, but rich micronations with high HDI have numbers that mess with things a bit. Currently Monaco's tech level is calculated as 2026-equivalent, and Liechtenstein's is calculated to be 2011-equivalent.
Regarding space travel, I'm currently revising the exact capabilities of the various planets.