This new life is still VERY new (to you too!) and change is confusing and scary. Mean is a shield for hurt and scared, just like us adults:)
Don't be very worried, but don't ignore... Give him, and each of your boys, a little extra love, touch/hugs and attention, maybe even just 5-min one-on-one for each boy each night (that's eons to them:)). Maybe get some books from the library (librarians are GREAT at finding things for us Moms!) you can share and cuddle all your boys in your lap to read and talk each night -- just a small bit and not too weighty -- about Mommy and Daddy, Change and Unconditional Love, that divorce is about adults, you would never divorce your children.
These small bits will add up fast, and even faster if you can share your "strategy" with your husband so he can put in his advice/share as well. You will both always have your children in common, so learning to act together for them even while distanced is a great way to transition and show your boys you both care for them no matter what.
When I was 3, my parents divorced and I regressed with potty training and would check to see if my father was coming to pick me up during the day. After a month, these behaviors went back to normal. My father never returned, but my mother never talked badly about him -- it just "was" and that made things easier.
Much love and great courage to share with your little men!