Welcome to the forum,
Let me fist start off with that fact that I am somewhat biased against Kimber.
That being said I will try to be helpful.
The 3" 1911 is not mechanically inaccurate, or rather it is not mechanically inaccurate at average self defense distances. It's harder to shoot well due to size and recoil, the laser will help you see that and help you correct it, but the same thing can be said for just more practice with the iron sights. With the laser you will see the dot bounce and jerk as you're getting ready to shoot.
With a 3" gun you are reducing velocity* and sight radius while increasing felt recoil and muzzle flip while decreasing magazine capacity. That's giving up a lot for concealability if you ask me. But if it means that the gun will be carried and not left at home, do what you gotta' do.
Regarding the 9mm vs .45 in a single stack 1911. I will offer two thoughts, a 3" 1911 will be easier to shoot in 9mm as there will be less muzzle flip and felt recoil. Second, if you only have 7-9 rounds on tap, I'll take 7-8of the .45s. I can handle the 3" 1911 in .45 just fine for the first mag or two. But if you're recoil shy, go with the 9mm. IMHO if you want a single stack 9mm, go with a Kahr, might as well ditch the unneeded weight of the 1911 for carry if you're not going with the .45.
I would take a Pro over an Ultra for the extra barrel length and one more round of capacity, statistically speaking the 4" is the more reliable gun. The 3" 1911 from ALL makers has a finicky history. Personally I HATE the 3" models. They just aren't that fun to shoot for extended periods of time, I'm not talking about 1-200 rounds at a casual range session, but prolonged shooting in the range of a 600+ rd weekend. They can get pretty tough on the hands.
*Regarding reduced velocity, see Ballistics by the Inch and The Box O' Truth #27 where sub-compact Glocks, the 26 and 27 were terminally out performed by the puny .32 and .38Spcl. in terms of penetration.