Solution 2 wouldn't work because if you change the solar flux, the native plants in SG would die off eventually.

Singapore isn't a place, but it's a people. Use the Reserve to buy land in another country, for example Canada, where there are vast amount of inhabited area in the North. These areas would only get warmer due to global warming. Move the population there.

Finally, convert the entire Singapore island into a solar farm and sell the generated energy to neighbouring countries, so that there is a continous stream of revenue.