I agree century timescales are tough, I'm not convinced 4 of 5 of your listed things have been solved.
Rubber has been replaced with oil.
Fertilizer has been replaced with Natural Gas that comes from the same place as oil.
Coal usage has been replaced/displaced primarily by natural gas, see above.
Wood, or deforestation, was a real problem in the 1920's, but many uses were replaced by plastics (oil) and natural gas. Sustainable forestry helped a ton here too once it hit the paper industry's bottom line.
Oil is certainly not solved, so we solved 4 out of 5 with the 5th.
Exactly -- that means that any analysis based on the current (as of 1926) 'reserves' or 'production capacity' for rubber/fertilizer/coal/wood would have been invalidated as soon as we switched to using oil instead. Imagine if instead of harvesting helium directly we find an economic way to split nitrogen (somehow, who knows). At that point, what you'd have to have forecasted would be the 'reserves' of nitrogen, which are functionally infinite.