I can relate to the stress of the selling and buying of the house. We've been getting deliveries from our storage unit abroad and the house looks like a bomb went off. Putting everything away, separating what needs selling, giving away and keeping is all consuming. However, the only way is through, it is a process that has a beginning and an end. Keep the eye on the prize. Won't make the stress disappear, but it will be more tolerable.
As for the kiddo. DO NOT. EVER. Blame yourself. You guys are doing the best you can with what you got. Can't give 100% right now? That's valid, do it when you can. My niece is a huracane, and her parents are on it 24/7. So maybe a little less screen time will help, maybe it won't. Allow yourself to be human, but don't add guilt on top of the stress. This is temporary.