The 230 grain UMC should perform just fine. I've used it with good results in quite a number of my 1911s.
The 230 grain bullet is pretty much the standard for .45 ACP. Lighter bullets may have less felt recoil, but I doubt that you'd find any significant difference in wear and tear on the gun. In any case, a 1911 properly maintain will be good for a couple of generations.
You would probably find that something like the Federal Premium Gold Medal Match 185 grain FMJ-SW load will have less felt recoil. But that will be primarily because it's loaded to a rather sedate muzzle velocity of about 770 fps since it's intended for serous target shooting. At standard pressure, a full power .45 ACP load with a 185 grain bullet will have a muzzle velocity more in the vicinity of 900 to 950 fps.
So while I hate to say this, you might want to consider that your groupings and accuracy could improve with some good instruction and practice. A Kimber 1911 with 230 grain UMC ammunition should be capable of delivering decent accuracy. Of course, it's possible that, since the gun is used, it may have been abused or messed with. You could try to check that out by asking someone you know to be a good shot with a handgun to try it out.
But a handgun is a difficult firearm to master. Most really good shooters have spent a lot of time and effort learning to shoot.
The first principle of accurate shooting is trigger control: a smooth, press straight back on the trigger with only the trigger finger moving. Maintain your focus on the front sight as you press the trigger, increasing pressure on the trigger until the shot breaks. Don't try to predict exactly when the gun will go off nor try to cause the shot to break at a particular moment. This is what Jeff Cooper called the "surprise break."
By keeping focus on the front sight and increasing pressure on the trigger until the gun essentially shoots itself, you don’t anticipate the shot breaking. But if you try to make the shot break at that one instant in time when everything seem steady and aligned, you usually wind up jerking the trigger. Of course the gun will wobble some on the target. Try not to worry about the wobble and don’t worry about trying to keep the sight aligned on a single point. Just let the front sight be somewhere in a small, imaginary box in the center of the target.
Also, work on follow through. Be aware of where on the target the front sight is as the shot breaks and watch the front sight lift off that point as the gun recoils – all the time maintaining focus on the front sight.
Also, while practice in very important, remember that practice doesn’t make perfect. It’s “PERFECT practice makes perfect.” More frequent practice shooting fewer rounds, but concentrating hard on what you’re doing, will be more productive than less frequent, higher round count practice.
Practice deliberately, making every shot count, to program good habits and muscle memory. Dry practice is very helpful. You just want to triple check that the gun is not loaded, and there should be no ammunition anywhere around. When engaging in dry practice, religiously follow Rule 2 - Never Let Your Muzzle Cover Anything You Are Not Willing To Destroy." As you dry fire, you want to reach the point where you can't see any movement of the sight as the sear releases and the hammer falls.
Finally, some instruction is always a good idea. I try to take classes from time to time; and I always learn something new.
Think: front sight, press, surprise.
