You should drill and tap the hole for the temp sensor before installing the diff cover. This way you don't get any chips floating around inside the diff.
Also on your lube return line to the diff. If you are using the top hole in the cover. You have to use a banjo fitting to have enough room for the wheel sensor. The elbow fitting is in the same space as the wheel sensor.
You should use AN 8 fittings and hose. The best pump is a Tilton continuous use pump.
Everything you been doing. I've done it.
You should read my build thread.
Rusty's Nismo Journal
Here's my diff cooler install thread.
MA Motorsports Diff Cooler Install
I installed an OS Giken diff when I did the diff cooler.
I installed the SPL solid diff bushing. No change in noise or vibs. Now when you change out the sub-frame frame bushings. It does increase. Because racecar.