Calculating Minesweeper Odds Is this calculation correct?

Everything seems basically OK now; the final result table seems to be correct. There are some minor isolated errors that don't seem to have affected anything else:

In your "example of a complete solution (S1-11+S2-11)", it should be $12\cdot4=48$ total cases, not $12+4=16$.

In the calculation immediately above "Results:", $(1/4)\cdot0.02620230228=0.02620230228$, the right-hand side isn't divided by $4$.

And in your summary of the results, I don't see why you say that MNO have the lowest marginal probability of containing a mine; from the table it's K with about $0.04$, and DEHL and SUY also have lower marginal mine probabilities than MNO with about $0.1$.

By the way, a good check for the results (that checks out) is to compute the expected total number of mines once by adding the marginal mine probabilities for all squares and once from the marginal probabilities of the total mine counts $5$ through $8$. The expected total mine count in the $25$ coloured squares is about $5.86$.