as a mother of a disabled daughter, I can only congratulate on what you are doing for your grandson.
I empathise with you, as professional people do not like to be questioned about what or how they are doing things. I know that from experience.
however, if you don't express how you feel about these things,
they will build up inside you and you will explode. sounds to me that you had every right to ask questions about these concerns you have.
keep up the good work on behalf of your grandson, you wont forgive yourself if you don't as obviously you have a wonderful relationship with your grandson. and he must be missing you.
I am not sure that having a break, nice as it might be, will help at this moment. just put on a brave smiling face and do what you have been doing. once this has all been forgotten about, maybe that's the time for you to take a break.