Figuring out Maaser Kesafim

After neglecting this for too long, I need to do an accounting of what I owe to Maaser/tzedakah.

I have multiple questions, I am happy to receive answers here, with sources, or just a book or reputable website with more information. I am in between rovs but iyh attempting to establish a relationship with a new one now.

1. Do I just take 1/10 of all my current money? I assume the answer on face value is yes.
2. Do I take 1/10 on money in a 401k that I don’t intend to touch for a while? I know I would take masser when withdrawing the money, but how does one deal with masser for retirement assets?
3. Going forward, do I need to give maser on my 401k contributions (this depends on 2 a bit)? I really hope not. The money comes straight out of my paycheck so I never see it and I save aggressively. As in, I contribute more to my 401k each paycheck than I take home (I am sick, kah, it may get worse so I want to prepare in case I must stop working).
4. How on Earth do people figure out where to give? Some places seem to say it can only go to feeding poor jews, specifically feeding, others say the mikvah is okay, but the shul isn’t, tuition usually isn’t, unless it’s a girl, then maybe. It’s all very confusing. Some though, say it’s just a minhag so in the case of need, all the above examples are okay.

I’d like to learn a lot more on this, especially the aspect in which testing hashem comes in, since it’s rare we are allowed to do that. Please recommend any information for me to read through