Middle names were not very commonplace among the lower classes in Wales in that period but were more commonplace in the USA. Many Welsh men who emigrated to the USA in the nineteenth century seem to have adopted a middle name after arriving in the USA; typically it might be their father's, or grandfather's or some other close relative's first name.

Howel / Howell / Howells / etc are all variants of the same name which is frequently encountered spelled differently depending upon who was creating the record. It was a quite commonplace name in south Wales, borne by around 1% of the male population in that period. Thomas was a very commonplace first name in that period. This combination will almost certainly result in there being a number of boys of this name born / baptised around the correct period in an area as large as a county, I'm afraid to say.

Good luck with your research!