Sounds like you should keep hitting the ranges, renting as many different guns as possible.
I'm under the assumption that buying one or two guns won't break the bank. So, here is what I would recommend. Purchase what feels good in the hand, knowing that as you gain proficiency over the next month or two of weekly shooting, you'll begin to see why it's right/wrong for you. At the point of 3mos, I think you'll have enough saddle time with it to know: will it work, or will something else be better. At that point, you'll have an inkling of
why that second choice would be better. That may sound an expensive way to go, but you can, for the price of a couple hundred dollars, simply sell out for another unit if you decide that another would be preferable. You need not be permanently saddled with a choice that doesn't fit.
Above all, know that you won't be carrying something that (a) doesn't feel right, (b) makes you wince about shooting, or (c) is so heavy/awkward that it's uncomfortable to carry. Pick something that matches your clothing choice and preferred mode of carry (IWB, OWB, pocket), as you'll want to ensure you properly conceal it.
As for caliber, there are lots of opinions on that. My backup gun is a .380ACP. I view it as an acceptable minimum. Not preferable, mind you, but there aren't a lot of other choices in 9mm that approach the size. A .45ACP isn't bad, either. The recoil profile is different than, say, a 9mm. Hard to know if you'll like or dislike it until you actually shoot a few. Each gun will behave differently in a given caliber, so try several.
If you haven't already handled these, consider them:
- Kahr K9, or P9 for weight-reduction. For me, the K9 is the most perfect fit to my hand, though the controls are tight and edges are sharp. With some tuning and a frame "melt," this would be one heck of a choice in single-stack 9mm format.
- HK P2000SK. Again, a wonderful fit in the hand, for me. One trouble is the magazine release, which is positioned such that I cannot generate sufficient force to eject the thing (thanks to an old fracture in the hand). But, it's small, concealable, easy to carry, easy to use. It's got an ambidextrous slide release and mag release, so it's suitable for lefties as well.
- Any of several 1911 style options, including: STI's Escort, Off Duty, Rogue and LS9; Springfield's EMP 9mm, Micro Compact; Kimber's CDP Ultra or Pro carry; Kimber's Aegis 9mm; Colt's original Officer's; any of a number of CCO-format 1911's (officer's frame with a commander-length slide), such as Para Ordnance's CCO.
- If the 1911 format grabs you, but perhaps the trigger layout intimidates you, consider Para Ordnance's LDA line of pistols. They've got a wide range of choices. One will certainly fit your hand. Consider the PDA 9 LDA or the Carry 9 LDA. Both are single-stack mites that are extremely easy to conceal. Both have the LDA trigger, for those that prefer to not have the standard 1911-style trigger system.
If you've ever held an STI, they can be a thing of beauty. If you ever get out to Arizona, consider looking up these folks:
Thunder Mountain Custom. They always have a large number of STI's in stock, so they can be great for handling different guns and trying them out.