Know that you have not failed. Everyday that you manage to get out of bed is another day conquered. It [censored]. Believe me I know. I have had days where I have done nothing but cry. Alone in this big house, without my children and my husband, I ask myself what is the point. 16 years of building a life that is now being taken away from me. Eventually, I force myself up. I force myself to do a meditation or a yoga class alone in my bedroom. I sort through clothes, I put on music very loudly, I clean cupboards. I force myself. Eventually it passes, and I remember I am FS. I was FS before him. And I was fine. Their is life after our spouses.
Plans will fall through. It is the nature of people. That is why it is important to get comfortable with being alone. At first the space will be immense. A massive void that can't be filled. But eventually, it will be your space - and you will, weird as it sounds, resent him invading it when he is around.
Re the phone call. It is early days. You will panic and will do anything to draw him back in. Know that nothing will draw him back in right now. Accept this but also accept you are human this [censored] hurts and hurt people do stupid things. I have done a ton of them. I have degraded myself in front of him, screamed and yelled at him and begged him to come home. I will tell you what I was told on this forum. You screwed up. Now get back on that horse.
Right now you need to heal. It is good that you are in IC. Use that to work through your pain. But, I would also suggest doing other things which have nothing to do with going inwards and exploring your emotions. Do something that gets you out there and gets your heart pumping again. Go online and see what groups are in your area. You need to find and do something that isn't about the pain, but about finding life again. Some here have joined groups that meet to play board games, others have volunteered at church or at shelters, and others have found groups that go for hikes or long walks. Find one and just go. I know it is way out of your comfort zones but go anyway. Once you do it, I promise, you will not regret it.
We have all been where you are. Breath. You can get through this. The rain [censored]. But rain is needed to grow. Weather the storm. The air will be fresher, the trees and plants greener, and the world brighter, when the storm passes.