Welcome to the family!
It seems you have a very strong desire to succeed, and that is essential to ones ability to grow.
If I may, though, comment on some of that which you wrote above. Note that I do this from love, not judgment nor hate.
First of all, 3 weeks clean is a massive accomplishment! God cherishes every moment we stay strong.
As well, it may be beneficial for you to make a smaller goal, like 50/90 days or something, instead of forever.
Regarding the ice baths/showers, it may be beneficial for you to examine what it is that’s driving you to want to act out, like stress, loneliness etc, besides the basic desire.
External things like baths are good for the moment, but in order to insure lasting change, we must deal with the underlying issues.
You ask how we overcome the “acute need” to watch bad stuff/masterbate.
The answer is, that one is successful when they realize and internalize that indeed, it is NOT an “acute need,” and that Man can function and lead a happy/fulfilling life without it.
Such a mindset shift is essential to lasting growth, and will do better in the long run then cold baths etc.
As you know, besides refraining from impurity, we are meant to add holiness in our life.
So I’ll ask, and feel free to not respond, do you have a connection to a Rabbi? Do you have fellow religious friends, or are you all alone? If possible, it would be most beneficial to surround yourself by those who share your mindset and goals so you can grow together.
There’s more to discuss, but I don’t want to over burden you now
Welcome again to the family, we’re proud and happy to have you, and may you be successful in all your endeavors.
YeshivaGuy