It seems to me that one option left re William and Hannah Richards(nee ?) is that Hannah Owen(s) in the 1889 marriage,is a widow nee Jones.She would,of course,still have to revert to her original/maiden name on the birth certificates from her second marriage("...formerly Jones.....")
I can' t find any reference other trhan the GRO to use with a local office,who might co-operate in telling you whether Hannah Owen(s) was a spinster or a widow.I don't think the GRO themselves would help in that respect.
Another speculative possible "coincidence".In 1911 there is a John Jones(from "Montgomeryshire"),of exactly the right age to be the brother of the Hannah Jones(Aberangell) previously identified,living in Wattstown,Ynishir,who has a son called John(Henry).Hannah would therefore be his Aunt-postcards?
Finally,the most wildly speculative of all,there is a disaster in Ynishir colliery in 1887,and among the dead is a David Owen aged 33(origins uknown to me).Could he be Hannah Jones first husband-there is a marriage in Aberystwyth district,2nd quarter 1886?
Regards
Roger