I empathize. I want to be clear that I think your anger is justified and normal. The machinery of capitalism dehumanizes by default and its operator's casual cruelty amplifies the impact.

That said: I'm going to skip over the rest of the context and cut down to your questions directly. I can't provide "do this" type answers because I'm not you. I can tell you how I think about it, what I do, and why. The first answer is lengthy. The other two are a bit shorter. I hope you find them helpful.

1. How do I handle my anger?

Step 1: Sit with it. Be angry. If I'm questioning the justification for my anger then I give myself permission to be angry anyway. This isn't the same as acting on it. I'm not giving in to my emotions. I'm not bargaining with them. I'm letting them really fully exist in me. Recognizing there is nothing wrong with feeling how I feel.

Once I've settled into this and accepted my emotions (and sometimes this takes a while) I can then decide if any action would be safe and helpful.

Step 2: I often find physicalizing intense emotion helps make it "real". This has to be a considered choice though. It's not reactive or destructive. I can beat up my mattress, take a hike into the woods and scream, make an effigy or a sign and burn it, go to a Rage Room and pay for the privilege of breaking stuff, etc.

It can feel invalidating to have emotion for which there is no acceptable expression. Finding a healthy way of expressing that emotion helps break down that false wall. Polite society is a very unnatural state (thankfully! Nature is terrifying) and we are ultimately natural creatures. This friction can be harnessed to create art and meaning but, sometimes, you just need to break some shit and be mad. That's ok. We still ought to be responsible about it.

Sometimes that responsibility extends to taking actions in the pursuit of fairness and justice. These are noble pursuits that should not be sullied by rash or vengeful acts. Organizing these efforts nets significantly more success than individual acts.

Step 3:

Start unpacking.

Am I enraged? Incensed? Disappointed? Betrayed? Anger is a rug pulled over the top of many other emotions. That's not necessarily a bad thing in and of itself. I do find it unhelpful when I'm trying to accept and understand myself better though.

Uncovering what the anger is built from makes our emotional scaffolding easier to see. Sometimes I use a thesaurus to find synonyms for the name of the emotion I'm already familiar with.

Identifying the component emotions helps me understand what my emotional state is trying to tell me. We feel what we feel for a reason. Understanding our why help us understand the impact of other's actions without requiring we understand their intentions.

Ultimately the answer for any unknown part of ourselves is self-investigation, acceptance, and curation. It is good and right to ask for help with every part of that process. When I run into something I can't accept and/or change then I know it's time to talk to a professional and build some new tools.

2. How do I avoid making my partner feel guilty?

Talk to them. :)

If I'm worried that I'm going to say something poorly or if I feel accuracy is key I will write out what I want to say ahead of time. I'm not so much writing them a letter as I'm writing myself one. Sometimes I write them a letter though.

Disconnecting initiating factors from their cascade effects after my partner and I have made a decision together is a very useful frame. Say we decide to go camping because my partner wants to and say I get injured during the trip. I can feel what I feel without regretting agreeing to the trip. I'm certainly not going to blame my partner for suggesting the trip. Bad stuff happens. That's life. Sharing the pain of the bad stuff is something I want my partner to do with me. Neglecting the reciprocity of that belittles our relationship.

3. How do I stop hating someone who has wronged me?

The opposite of love is not hate but indifference. Hate is empassioned. It burns and writhes and lashes. It urges us to demonize and conquer. I'm not sure what the opposite of hate is, exactly. I think it's something close to disappointment.

I'm reminded of Paulo Freire's Pedagogy of the Oppressed. One of my most memorable takeaways, in my own words, was that if we're to escape the self-sustaining cycle of human abuse we must realize that in dehumanizing us our oppressors dehumanize themselves as well. To Freire's mind the only successful revolution is one in which the oppressor is re-humanized as well as the oppressed.

I have trouble imagining myself feeling sympathy for those doing evil things. When that gets in the way of me letting go of (arguably justified) hatred I think of my younger self. Would I hate that person for being small-minded or callous? Maybe! A least for a moment. Then I would remember they have so many things they don't know yet and so much growing to do. It doesn't excuse the harm done. It nets me a better perspective on how much potential people can live up to. That helps me avoid hatred. When hatred fizzles out I find I'm left with disappointment and sometimes disgust. Those don't lead me to dehumanize someone. I think that's a good start if nothing else.