I don't see why you would need to touch the diff when replacing the rack but that's the only explanation I can think of as to why the diff fluid is low.
You do need to remove the oil filter assembly though and if they didn't replace the o-rings then that would explain your coolant leak.
Interesting, seeing as there are no leaks from the pinion or output seals, I'm inclined to believe it was either under-filled (unlikely as you seem competent) or someone had drained out most of the fluid when replacing the steering rack.
I've not replaced my rack before but its possible they...
I don't believe that would be possible, the main bush has a locating nub and the two lower bushes sit in a recess on top of the wedges, there wouldn't be enough clearance to install them without pulling the column from the tube.
You shouldn't need to drill anything, those shear bolts are what hold the steering lock onto the column (as well as the column tensioning springs/ramps).
The springs are behind two in-hex screws/caps.
I did not need to touch those shear bolts when disassembling my rack.
I backed mine out in order to reduce friction to aid the aging telescoping motor, subsequently it's working great but has some radial play.
In order for you to further tighten your steering column (remove play) you may have to place something to shim up the existing springs as the bolts are...
Replaced my original radiator (along with the heater Ts) as it was starting to develop tiny cracks on the top with another genuine one 16400-50360, got it for a surprisingly reasonable price from the Lexus dealer in Adelaide for AU$650.20.
I think your best bet is to replace with OEM AHC TBs and rear springs, I'd suggest putting up a buy request in this forum and hope someone is parting with theirs in an AHC delete mod, maybe even the wreckers will sell them for a fair price or FB marketplace.
You could go with the rear Kings...
Holy moly, yeah those springs are way too stiff.
Did you keep your original AHC springs?
Make sure you follow the steps on the first page, once you've cross levelled, set correct height all round you wind your Torsion Bars (TBs) as many times as you need to achieve correct pressures up front...
Just replaced my heater Ts and I'm glad I did because it didn't take much force to snap the base off one of the Ts; I did have to slice the hoses to the firewall but the others just twisted off.
I used the following part numbers.
96134-42100 x 8
90467-19022 x 4
87248-60460 x 2
87245-6A210 x 1...
I'm not aware of any way to manually disable the auto tilt/tele without disabling the system completely.
Have it set to where you want and unplug stuff as has been previously mentioned but if you want to adjust it again that would be annoying if you share the car with other people.
I would...