Yes, the P89 will fit in size #HN45BR.
Yes, the smallest Elite Survival Systems Military Shoulder Nylon Holsters w/Adjustable Strap is designed for 4" revolvers and larger automatics. I would recommend the Condor Universal Shoulder Holster, found by using the link below:
https://www.opticsplanet.com/condor-condor-universal-shoulder-holster.html
The Elite Survival Systems Military Shoulder Nylon Holsters w/Adjustable Strap (HN45B) is designed to fit most Colt 1911 4.25-5" and Browning Hi-Power. HN45BR will fit most 4" revolvers and larger automatics, HN45BL fits most 6" revolvers and long barreled automatics. And HN45BXL fits most 8" revolvers.
The universal one should.
Yes you would need HN45BL
You would need HN45B
That is correct.
Yes it should fit just fine.
Unfortunately that specification is not provided by Elite Survival Systems.
Unfortunately they do not make a version of this that would properly fit the Taurus Judge.