It's hard to answer all these questions, because a lot of them are specific to the individual.
For example, where on your person are you going to carry? That will affect how big of a gun you can carry. Lots of folks carry full size autos IWB. I personally carry a USP Compact .40 IWB. I also don't buy into the theory that .45 is significantly better than .40 when you're talking about shooting JHPs. If you're talking about carrying IWB, I think you can easily carry any of the guns you've mentioned.
Have you had the opportunity to shoot the guns you're considering carrying? You can hopefully find a range that lets you rent pistols and try some out. The most important factor when determining gun maker, model, and caliber is your ability to shoot the gun you decide on. Everybody's hands are different, and everybody perceives recoil a little differently.
Are you looking at the LEM or DA/SA variants of the P2K and P2KSK? I suggest you try the LEM before you buy it; it's a love / hate thing. I hated it and sold my P2k.
You're considering a Kimber, but many folks new to pistols are hesitant about cocked and locked carry. Be sure you're OK with that. There's nothing wrong with it, but it tends to intimidate some new shooters, even though they're OK with the glock for some reason. I carry my USP Compact cocked and locked and it doesn't bother me one bit.
Finally, since this is your first pistol, I strongly urge you to get proficient with it before you start to carry it. You need to know that you can use it adequately to defend yourself, that you can handle it safely, and that you won't send bullets towards innocent bystanders in the event you have to use it.
Oh, and save yourself some money -- get Milt Sparks holsters for IWB carry. I recommend the Sparks VM-2. You can get it from
lightning arms, based in beaverton, OR. Or you can call sparks and get on the waiting list.