Anxiety Support Group
Anxiety is a physical condition marked by intense and persistent feelings of distress, fear, angst or dread. General anxiety caused by routine day-to-day stresses usually passes quickly and is experienced by almost everyone at one time or another. However, such feelings that linger over time and are very difficult to cope with, and which lack a clear cause, may indicate...

Is there a reason why your grown son has to live with you? Does he work? It sounds like he is a big contributor to your anxiety, so I am just wondering why he is living there with you and your husband still. And if different living arrangements might help your situation to be less stressful for you.
You are doing the right thing to reach out for support, understanding, and acceptance.
With your adult son, he has to learn control of his emotions and accept that he is responsible for all of his acts, responses, and reaction. You are NOT responsible for what he says, does, and acts.
He lives with you. You are NOT living with him. As a primary caregiver for your invalid husband, you deserve a break and peace and calm in your household.
So you had a meltdown. It probably scared your son. When you are both calm, have a conversation (work it out in writing so you are prepared to be calm no matter what he says, feelings are not part of the deal-he will pick it quickly when you keep to evidence only).
I've been there, done that, and it's not an easy path to finding a better balance that works successfully with everyone finding the best way that works for their situation.
You are not alone in this. Take time for you, even if it's just a few moments and walking outside to view the stars and moon or sunshine.
i was able to run away from my middle aged son in 2017 powers greater than i evicted him from the house i still own in 2020. last heard, he was still homeless. i still maintain a safe social/physical distance from him, but? ? ? i miss him terribly. i'm still praying for a miracle. just praying. . .
wish i had easy answers for all of us. just wishing. . .
be gentle with all the players involved and patient with the process.
hope healing happens here.