Sophia A Richardson in the Galveston census turns out to be Sophia J and there's a likely birth of a Sophia Jane Richardson in St Marylebone second quarter of 1840 Vol I page maybe 122 or 212. It's illegible. And there's an Annie Richardson born in the third quarter of 1841 in London Vol I page 119 and a David Richardson born in the first quarter of 1844 at Marylebone vol 1 page 145. These correspond to the census ages in Galveston 1850 of 11, 9, and 7 respectively.

None of the Eliza or Elizabeth Oates' in the marroage index on Ancestry for the years I checked which were '37, '38, '39, '40 and '43 and '44 cross referenced to a David Richardson.

But that's a lot of searching and cross searching and I may have missed something. Eliza was 28 in 1850. Which means only 17 when Sophia J was born.

Sounds like an interesting family. More power to you in tracking them down.