Datalogging ABS sensors will rule out any interference
Only need a new loom if you upgrade to the newer generation of rack (Gen3) which is less likely to fail, the Gen2 that most of us have is very prone to failure but is a straight swap. An adaption procedure is needed however when fitting a new rack
A new genuine rack is north of a grand, a recon unit is around the £250 mark plus a couple hours labour.
The steering weight will vary, its an electromechanical unit that isn't the quickest to react. What you describe could also be the infamous subframe creaking that plagues this platform of cars. Worth a search