Hi, Tac. I've lived in Colorado Springs for the last nine years, but spent February through June in Little Rock, Arkansas in both 1994 and 2005. Additionally, I've been TDY to Little Rock numerous times throughout the year.
Is Arkansas humid? You bet. But it's not as bad as New Orleans, S. Korea, or Jacksonville, Florida, three other locations I've lived for two or more years. In fact, I found it to be rather pleasant throughout most of the year.
As for gun culture, my first time through I brought my weapons with me, storing them in a safe in the off-base hotel for four months I went shooting with friends on several occasions at a local range. Arkansas has straightforward CC permit laws and is a "gold star" OC state - no permit required. You can't OC in an airport and some other areas, though. I guess even in Arkansas, sometimes the locals can be skittish.
As for the local culture, I always felt welcome by others. It's Southern, so the hospitality factor is up there, but it's a bit hard-working, too, kind of like "Show Me" Missouri.
As for Fayetteville, I can't say, but I did live in a college town myself for seven years. Yes, the young adults dominate throughout the school year, but it's dead during breaks and very low-key during the summer months.
As for retirement, I suggest you Google something like "Cost of Living City Comparison" and compare it to several other cities in which you've lived or were considering.
Do get up to
Gaston's White River Resort. It's the heat!