Trouble starting, ABS light on

My battery is only a couple of years old. Last week my SUV sounded weak when starting. Then I had to get a jump cause it just clicked. The battery cables were nasty so I cleaned them and it has been okay a few days, but the ABS light stayed on for several days. Then the weak starting again. Now there is a rumbling noise on the driver's side in the tire area only when turning and the ABS light came on but is now off. I used an Innova 3100 diagnostics tool just now and when testing the ABS it was in the red and showed U2023. I have had my SUV four years. I haven't had a tune up. I have had the front and rear brake pads replaced and I try to keep up on oil changes but full maintenance I just do not have the money for. Six months ago I lost my reverse gear and my emergency brake release lever broke off. My oil temperature gauge does not work but I do not think that is part of this problem. Is it my bearings and hubs? I know the bearings are sealed. My suspension squeaks going over speed bumps and there has been a clicking noise in the right rear for a while that you hear only at very slow speeds. Is the turning sound my transfer case? I do not have much money so I really need help pinpointing what actually needs immediate attention relative to the trouble starting in conjunction with the ABS light and the U2023 code reader. Thank you so much everyone.