Hunts Marriage Index doesn't include marriages in Tempsford, which is, and has always been, in Beds.
The 1732 alleged marriage on the IGI between Richard Wallis and Sarah is a member submission, not extracted from Tempsford parish register. All member submissions should be regarded as suspect. Only extracted entries are reliable. You've just found out why you should place no reliance on member submissions. However Richard and Sarah Wallis did baptise Sarah Wallis in 1736 in Tempsford. And there are four extracted baptisms of children of Adams and Sarah Brace in Tempsford 1746-57. But there's no burial of a Richard Wallis in Tempsford before 1746
Does anyone know why an IGI entry would only give the spouse first name ??
Because it's fiction submitted by an LDS church member
Marriage certificates only started in 1837. Marriages prior to this are simply entries in the parish register, and marriages prior to 1754 only usually give the names aof the bride and groom, and possibly a parish of residence if you're lucky.
The Adams Brace marriage is also a member submission so needs checking against the parish register to see if it's real. There's no Adams Brace marriage in Hunts 1701-54, nor a Richard Wallis to a Sarah.
What exactly are you looking for, and what's the oldest proven fact that you have?
David