And second, the already posted link shows that within a particular range of temperature and CO2 concentration increasing them increased the world's GDP. We are not at the end of that range so increasing the temperature and the CO2 further would get us closer to optimality

It takes some time for added CO₂ to exert its full effect on temperature. Because of that lag, I'd expect CO₂ levels to hit their optimum before temperature does, so it's worth considering them separately.

-- meaning we're not there yet.

The results at that link and in its underlying source suggest we're at (and maybe beyond) the optimum CO₂ level already. According to that paper, the temperature won't reach the calculated optimum of 1.2°C to 1.3°C until 2025. But the CO₂ level is already high enough that we're likely to overshoot that temperature unless we cut emissions aggressively.