Sounds very good, AMBLY and Debbie, very good indeed. As you say, AMBLY: "Everything - right down to his occupation in 1910 US Census, to the fact he lived in a family owned pub in Merthyr, had at least 1 son died age 19 in WW2 - points to your Frederick James PRICE being the same man who stated on his US WW1 enlistment as having been born in June 1890 (5 years older than you believe he should be) and to his being the one who appears in the UK Census 1891 and 1901, and who immigrated via New York to Des Moines, US in 1908."
My dad used to talk about Des Moines Iowa when I was growing up. And so I think, as you say, "I don't think you could get any hotter match than what has been found!
The age (b 1890 as opposed to 1895) is the sticking point, but I'm going to give that one a miss for now. I'm going to run with this information for now and say "congratulations" to both of you--and with a great deal of appreciation. I will now take it from here after I get a good sleep.-Ron in Tasmania