As has been said, you need to speak to the management about how you are being treated. It's not acceptable for them to treat you as a naughty child. Think about what you want, (to be treated respectfully as an adult as is your right) and how to ask for that in a strong, respectful way before you ask for a meeting.
(eg, I've asked for this meeting because I am unhappy at the way your staff are treating me. When I try to help my husband they shout at me / belittle me / insert your concern. I'm sure it's because they are very busy or maybe they are worried about my safety, however; I need them to treat me as an adult and explain their concern / tell me what I can do and how to do it safely. That way we can work together for his benefit and I can be supportive. At the moment is feels as if we are on opposing sides which is obviously not good for anyone. ....
You do need to have a bit of confidence in yourself. Keep reminding yourself you are an adult and deserve to be treated as one. This whole situation has, understandably, made you feel powerless and fragile and small. It's easy to be bullied when you are feeling that way. Their behaviour is not acceptable in any instance.
As for the nurses belittling you: This process is very hard- especially the first time you do it, so maybe practice a bit on your own... when the nurse "tells you off" like a child, you take a breath, try to be calm and imagine yourself growing an inch or two. Then you calmly look her in the eye and say some or all of this: (to yourself as much as to her!)
"I am an adult, I am rational and can follow logic. If you want my respect, you need to treat me as an adult and explain how I can help. Being negative doesn't help either of us." (don't wither, don't blame and don't apologise)
The nurse will probably get huffy but it will make her think twice before she treats you as a child again. You may have to repeat this each time it happens, but it will work eventually and is more empowering than allowing yourself to feel small and going home to cry. (I do know how awful this situation is, I've been there and cried my own river too often)
If she is cooperative and respectful, then you can calmly ask "what would you prefer me to do when my husband needs xxx (insert help required) and you are too busy to help straight away?"