An entirely new loom seems excessive for the faults you are encountering.
1.Rear lights can do strange things if the taillights are not earthed properly - usually just means the screws holding the taillights on are not tight.
I have done away with the factory screws and replaced them with bolts which I cranked down like a goddam mofo so no earthing issues (and erratic taillights) for me
2. Is your CHMBL not working? - this is usually due to the wires to the contacts falling off - pull down the rear-most part of the drivers side rear fender liner - reach up and feel for the back end of the tub contacts - I'm guessing one or both wires have fallen off.
The wires need to be pushed back on with some authority or they will fall off again - I feel a definite 'click' when they are connected properly.
Doesn't matter which wire is connected to which contact.
3. Dash lights - is your dimmer turned down?
4. CEL - This could be coming on for dozens of reasons - you need to extract the codes to determine why it is coming on.
Google 'key trick' to display fault codes in the odometer on the dash.
Note - if you have a 98, 99 or 2000 TJ, the 'key trick' will not work and you will a scan tool to extract the codes.
If your TJ isn't a 98, 99 or 2000 model, I can describe the key trick here if you want.