There are some special countermeasures that I sometimes use against certain torpedos. They don't always work though. That's top secret
The best way to evade a torpedo is to A) Know where it is, B) Know where it came from and C) Know where it's going. There is no point in evading if you can tell it's clearly going north when you are in fact 10 miles south of it.
Likewise you should not trundle along in a torpedo's path when it's coming toward you.
So here's what I recommend when you receive a TIW message. First, turn 60 degrees to the bearing of the TIW. Try to locate it on any of your sonar sensors, or even your active sonar. You might as well make a few pings, someone knows you're there if you got shot at. Once you've found it, try to determine whether or not it's coming at you. You will need to do this within about 2 minutes or less of TIW. That means you have to rely on your sonar skill, not the auto TMA to determine where the torp is and where it's going.
If it's coming at you, turn to a heading that is exactly opposite of its current bearing to you. You want to head away from it as fast as possible.
Now there's a couple things to keep in mind, you may have a wake homer, a passive torpedo, or an active torpedo heading toward you. If you are in multiplayer and have a sub on your team, ask them if they hear pinging. Otherwise, assume that there is an active torp out there and take measures against it.. PM me on how to do that.
There is an evasion method posted by either SeaQueen or Sea Demon for evading wake homers. You might try that method, What I usually try though is getting as far away as I can, then make a 90 or greater degree turn and slow to 4 or less knots, travel at that speed for some time, then accelerate away in a different direction. Don't cross your old wake or the torpedo will lock in on the strongest (closest to you) wake.
For passive torpedo's it's pretty simple. Get far away then slow down, put your engines to stop or 1/3rd. Listen in on it every once in a while to see if it's following you.
As for the nixie, you need to reset the nixie every time it gets hit. So if you have two torpedos coming in and one hits your nixie, make sure you retrieve it and stream it again if you want it to save you again.
I'm not sure if nixie explosions kill the towed array but it might be worth retrieving the TA to a short length just in case. If you're sure a torp is going to hit you, you can retrieve it fully.
Lastly, you should generally fire a torpedo down the bearing that you are being attacked from. But this really depends on the kind of torpedo shot at you. An akula can launch an attack from pretty far away, so it may be a waste to try, better to use your helicopter to attack that bearing. Just have it make a ladder of vlad and difar buoys and the contact will eventually show up.