As the torpedo is nuclear, merely resisting the explosion is a no-starter.
So you need to make the torpedo not explode near enough to your ship to do damage.
Before you can do anything to or about the torpedo, you need to know of its existence.
Fortunately, a torpedo barreling along at 75 knots is very noisy. In addition its guidance is active sonar (passive does not work at that speed), so acoustic detection should hear the torpedo coming from many kilometers away.
Option 1) Destroy it
- The incoming torpedo is noisy, and its destination is known. Intercept it with your own anti-torpedo-torpedo. Your counter torpedo will be shorter range, and need not be nuclear, so you can afford to send out dozens of them.
- Alternate: locate the incoming torpedo, drop your own nuclear airborne missile directly over it. As the missile is a magnitude faster, evasion is not an option. Expensive and messy, but very very likely to work on one shot.
- Close-in defense: deploy a couple (of thousand) tiny drones to swim alongside your ship. These drones are just a fast swimmer, a proximity detector, and a small High Explosive charge. Basically, small smart depth charges that accompany your ship. Have them swim out as far from your ship as they can while still maintaining a 100% overlap in detector and blast-lethal-damage range. When the torpedo approached such a drone, it determines when the torpedo is close enough, and suicides.
Option 2) Divert it
The torpedo is guided by sonar.
Just redirect it to one of your suicidal drones by transmitting a suitable Spoofing signal.
Better yet, hack its "broadband direct control secondary backup" and tell it to return to sender.
Meanwhile, you now have an accurate source for the origin of the torpedo. Send a mr. Bomba to greet the interloper.
Realistically, you would not entrust a nuclear warhead to a longrange 75-knot smart torpedo.
75 knots is way too fast to be stealthy, yet not nearly fast enough to evade interception and retaliation via speed.
Either make your smart torpedo very stealthy, with zero propulsion noise and with a sound&radar-absorbing/deflecting surface, so that it can sneak up on the target,
Make it so ludicrously fast that countermeasures are unable to be mobilized in time.
The russian Shkval, for example, approaches at a leisurely 370km/h. (and that's using 1977 tech)