Interim update: We isolated two products by chromatography from the second synthesis. Both are probably sulfonyl phosphonates on the basis of their P-31 chemical shifts. One is close to the product of the first synthesis, but there is an extra signal in the H-1 NMR that has a chemical shift (2.07) and integral consistent with an acetyl methyl group, CH3C(O)-. The other product has two very broad, non-Lorentzian peaks (near 2.5 and 1.8 ppm), each of which integrate to 1H. I don't recall seeing anything like this. On the other hand, there is an indication that the (EtO)22P(O)CH2- portion of the molecule is intact.
Time permitting, we plan to look into these questions further in the next few days with the following limitation. If a compound is not our desired compound, its identity may help us learn how not to make it the next time we perform this synthesis; we will not pursue learning about its identity further than achieving this goal.