Your first graph shows diminishing returns for both battery storage and solar. It's also not clear whether that's the marginal cost or includes the capital cost

Your first graph shows diminishing returns for both battery storage and solar. It's also not clear whether that's the marginal cost or includes the capital cost to build the structures and all the infrastructure. To compare nuclear against solar you have to compare it against the sum of the cost of solar plus battery storage. Investing in solar/wind/nuclear energy sources, storage, and research for improving all of the above seems like the best strategic option for at least the next decade.