Money Gained from Haram Source Before the Earner Knew it was Haram

To respond to this, we would just cite the fatwa of Dr. `Abdul-Fattah Idrees on a similar question, for it suffices. He said:

As you did not know the prohibition of working in such places, you are allowed to make use of the money you gained during this period because you exerted effort in return for this money unknowing the prohibition of its source. Therefore, it is permissible for you to spend it on your preparation for marriage and the like lawful purposes.

For sure there are many other sources of lawful earnings. You and your father can look for any other job even outside that field which, as you have mentioned, is difficult for you to observe the injunctions of your religions when working in it.

As for the zakah, if the money you saved in this period has reached the amount that is zakatable, then you have to give out its zakah according to the percentage prescribed by the sharia.