In this case, he would probably put on quite a bit of embellishment to the way he talks, sort of characterizing himself. You're looking for someone who takes inspiration from Sam Elliot:
Texas born and bred here, fourth generation even. The frequency of the word "howdy" varies from region to region. Remember, it's a big state. Here in West Texas, you hear it all the time. Hell, I use it frequently myself, but I'm being at least a little ironic or whimsical when I do it. You'll hear it used that way a lot, but if you aren't wearing the hat and boots (or cowboy cut jeans and a tucked in plaid straight from the farm,) and use it seriously, it seems completely out of place. A thicker accent goes a long way in legitimizing it's use. I especially use it when I travel. By most accounts, my accent only shows through on a few words, but if I'm in Illinois, it thickens in this almost involuntary, territorial way. Suddenly, "Hi. I'm Todd" becomes "Howdy. I'm Todd. I'm from Texas," in an accent approaching that of my cousin who wasn't allowed to answer the phone at the Chinese restaurant where she worked, because people were sure they had the wrong number and hung up. Last thing, if he says howdy, and he has the accent, and he isn't being ironic, then he won't pronounce the "W". There's no diphthong. It's more like: "Haddy, ma'am." You shouldn't spell it that way, of course. I only mention it in case you want to explain what's being heard by other characters, much as Stephen King does every time he has an old New Englander speak: He said "over yonder," but it came out "ovah yandah."
Well, the rest of y'all forgot to designate a second person plural pronoun, so we conjured up a contraction to fill that particular void. It's perfectly grammatically correct, in my opinion. Slightly more questionable is the possessive form: "y'all's." I'm sure some people think I'm joking, but it's a staple in the lexicon: "Is everyone headed to the club, or are we all going back to y'all's house?"
Y'All : Singular All Y'All : Plural Y'All's : Possessive All Y'All's : Plural Possessive It's not questionable. It's just the way it is.
Not much of a worry, he's got like three sentences lol The Irish character plays a major role in the book, but I'm beginning to think Ireland is a myth, and that Irish people don't really exist xD
The character is a bar/restaurant owner in a foreign Asian country so theatrics is a part of it, and yes, he's wearing a Stetson lol. How do you think a forty something year old man, such as himself, will refer to a stunning, twenty something woman? Ma'am doesn't seem right at all lol
You have to go with your gut on that, but I could see any number of Texan semi-stereotypes saying ma'am, not just cowboys. That's hardly universal though. I never say "sir" or "ma'am" unless I'm standing before a judge, so... It would all depend on character and context. If you can't hear him saying "ma'am," trust that instinct. Drop a line or two. Give me some context. "Refers to as" can mean so many things. What's the line you have in mind with "lovely ladies" in it?
There’s more than just 3 Texans here. I can quite easily see a Texan in a foreign land exaggerating his “Texan-ness”, if that’s a word. Like Rzero, I do that myself and I never lose the “y’all”. Up here in the Panhandle, people under 40 are more apt to sound like young people on tv, the more rural folks less so but still more than those over 40. You might watch Man of the House - the one with Tommy Lee Jones. It’s a bit exaggerated in its portrayal, but really not that far off. Tommy Lee is from south Texas.