@Ginger89 i personally do not feel it is solely down to you , if you tell his family about his behaviour. His mum may be a source of his anxiety but you could reach out to his extended family. That should not be a reason for you failing to reach out to his family.
I have lost friends in my 20's and 30's, due to mental illness. Illness that i and others dismissed at the time. I am 50 now, so wiser.
Being " fond" of someone is not a basis for a relationship. Being " in love" is.
You are not in love. You are "fond". Take your DC and build a new life for yourself. Support yourself.
Let your DH's extended family know about his heath anxiety issues so they can out in place an appropriate care plan for him.
If he were my son, i would want my family to understand what he is doing. So that we can all support him. You may not love him, but his family will and they will want yo safeguard their sons mental health in the long term.
Op, i would focus on building a financially stable and independent status of my own for me and my DC. If i i were you,look after yourself and your DC. Focus on you and your child for now.
Leave DP to get help from his family . Build your own independent life OP.