We are 4 months post initial disclosure (the rest came out in stages. Two months since the last and final disclosure).
4 months out in affair terms is still considered "early stages" for most folks. Both he and you seem to be where most people are at in the 4 month timeline. It is VERY hard for everyone involved, and you are doing a good job by doing your best to not get defensive with him. One thing to understand about your BH at this point is that, not only did you lie to him and betray him by having the affair, but since you TT'd afterward, it only continued to hurt him, and showed him even more that he cannot trust you. Please don't feel that I'm picking on you, most WS's have a similar story, myself included. Imagine for a moment that someone came up to you out of the blue and punched you so hard in the face that you dropped to the ground in a haze. You turn and see that the person who hit you is someone you trust implicitly. Just as you are still reeling from the pain and asking them why the hell they just hit you, you see their shoe come up and clock you in the chin again, and then a few minutes later, a stomp to the ribs. That's just a little bit of what it feels like to the BS when everything comes down. Not only did their loved one take them down and out viciously, but then each TT is like getting hit again while you're still down. At this point, he'd sooner trust a stranger walking down the street than trust you, because at least the stranger hasn't betrayed and lied to him over and over. That's a very bitter pill to swallow. The first time someone said something like that to me, my jaw hit the floor as I started to understand what they were saying and what I had done. Understanding how your husband is feeling right now is imperetive to healing.
When my husband is angry and flooding with pain and rage. I don't want to make it about me...this is about his pain. But I feel like I am nothing as he rages at me for what I did to him. And how much I destroyed in his life and how he's suffering unbearably. I own all of this but I am helpless to help him. And he tells me he is no longer attracted to me and sex with me disgusts him.
Not making it about you can be very hard at first, but it is very important. I still struggle with this quite often myself. For most WS's, it is our own self-focus and lack of self-value that leads us to stray in the first place. Now we need to learn and lean on other skills in order to try and save both ourselves and the marriage. This can be very hard to do with your BS because shame and guilt cloud our thoughts as the person who hurt them, and those feelings lead us to focus on our own pain and needs. Try to pretend that your husband is someone else that you care about deeply, maybe a child, or a sibling, a best friend or parent? When they tell you about something hurting them, do you tell them about how YOU feel? Or do you ask them more about how THEY feel and listen to their pain? Your husband wants to know that you really, truly "get" what you did to him and how profoundly it has hurt and changed him forever. He also wants to know that you "own it" and will do all you can to change into the person he thought he married in the first place.
For what it is worth, my wife also goes into phases where she sees me as the most disgusting and vile thing that ever walked this earth. Sometimes it lasts for a few hours, sometimes a few weeks. It is painful when that happens, and your spouse may truly hate you in those moments. My only suggestion is to give them some time and space, and keep doing what you normally do, try to put them first in all things and work on bettering yourself by working through IC, reading books and articles, and coming to SI. Just assume that sex and affection are off the table for now.
He asks me unanswerable questions...like how can I trust what you say?
He can't, honestly. And it is okay to say that to him. At least he'll know you're being honest and not just blowing smoke up his ass. But the real answer to this is - the same way you got him to not trust you. By your actions, and consistency. Nothing you say to him now matters, and I mean that literally, because he's learned that he can't trust you, so he assumes everything is possibly a lie. It hurts like hell, but it's our own damn faults. Anyway, the way to earn trust back is to show him through your actions that you are fighting for him, and able to handle things that you didn't handle well during the affair. He needs to see constant work on your end, such as being transparent in all things, going to IC, predicting triggers and helping him prepare for them, getting rid of things the OM gave you (with your BS's knowledge) and offering affection and intimacy whenever he is ready for it. He wants to see you putting more effort into winning him back than you put into having an affair. If you really wanted to meet up with the OM during the affair, you would have found a way to make it happen, and he knows that. Now, he wants to see you put that same tenacity and effort into healing him and winning him back. You are right, it is near impossible, but still possible, so you need to find a way to do it.
I need to help him. But I feel like I can't.
You probably can't right now. You can't help him right now because you are too broken yourself. It's like the old, "You can't clean a dish with a dirty dish towel" adage. You need to go figure out what events in your life and in yourself led you to a point in your life where you could allow this to happen, and work on changing yourself into someone you are really proud of, and love. He has his work to do to, on himself, and you cannot remove his pain for him any more than he could do the same for you. What you CAN do however is do your best to not make things worse, and to simply be there for him, to hold his hand as he gets through this. Let's say you accidentally knocked a child off a bike, and they fall down, hurt and crying. What would you do? Most people would help them get back up, kiss their boo-boo, help them pick the bike back up and see if they can help them get back on that bike again. (See how it's all about them, the people we hurt, and not about us?) Do the same for him. You may feel buried in shame, and it is okay to tell him that, but try not to let it stop you from being there for him. Otherwise, even our shame and remorse still ends up being about us.
I need tools now to help him
The book that ThatWillDo recommended is a great place to start, as is SI. Look in the top right corner, there is a link to the "Healing Library", read everything there. It sounds like you had several affairs, so you might also want to go to an SAA group and share some war stories with the people there. I always recommend "Rising Strong" by Brene Brown as a good book to read even though it is not affair-specific, it is great about learning to be your best self.
Good luck.