L.R.
You say your therapy seems to be working. No it isn't. You have two children, not one, and the bigger child has a jealously problem.
The therapist needs to hear all this. And you and your husband need a second session each week: A parenting class. Seriously, he is undermining you; he does not understand that a sick toddler is always going to be clingy; he expects a recovering child to "make eye contact" when the boy doesn't even understand those words; he wants a perfect child and wants you to parent HIS way.
Please, please see the therapist and say that therapy is not helping your parenting in this home and bring up these issues of jealousy (of your husband, jealous at the attention you get from your son) and outlandish expectations (from your husband, who seems to think a toddler is "dissing" him somehow and who clearly has no idea of what to realistically expect from a young child's behavior or emotions).
You said it yourself -- Husband thinks that therapy will bring "magic overnight" and does not recognize that his travel schedule means he is largely an occasional boarder in his son's mind. The one kernel of goodness here is that your husband was talking the language of therapy -- "we need to talk about this" -- but IN therapy you both should work on his learning WHEN to use that and when to recognize that you are overwhelmed and just need immediate assistance with your son -- not a lecture or discussion.
Please get to the therapist and explain that this is all not working.