OP, I went through the thinking that you are saying you are in. I also was a student of Rav Shalom Arush for 3 years, so I know his teachings rather well.
The issue is that you are trying to figure out how things can be good. However, emunah is for when you CAN’T figure out how things are good.
In other words, if you were to “know” how things were good, then that is knowledge. However, if you were to “believe” that things were good, then that is emunah.
By the way, as I mentioned, I know Rav Arush & his shita very well. And he constantly says that the only way to achieve emunah is through talking/praying/hitbodedut to H-shem every day. It’s not an option if you really want deep emunah…and trust me, he is someone that has amazing emunah. He does NOT have an easy life at all; he still goes through all the situations that normal people go through. But he always has a true smile no matter what happens & he has many miracles happen for him because of his emunah.
Either way, your questions are quite normal for anyone starting off in their journey of finding/understanding emunah. Also, I should add that I heard a huge tzaddik in Jerusalem saying that this generation is only “payback”. He said that all the problems one experiences in this life are just payback from previous generations so that a person doesn’t have to pay the price in the world to come. For instance, if someone steals from someone, then he was only stolen from because it’s mida k’neged mida & in this way, it is a benefit for the one that has been stolen from, since he doesn’t have to worry about the punishment later on.
I hope this all helps.