Pet, your feelings are entirely natural. When he was 16, my son with severe learning difficulties had to go to boarding school. My doctor insisted, my health was in ruins. My mum spent her last year in a nursing home. Like your husband, her needs were simply too high for any other option.
It will take a long, long time to get used to this new situation, so put your brave face on, do what has to be done, but be kind to yourself, and look after yourself.
It's OK to cry when you get home, in fact, it will probably do you good to let out all the emotions. If you feel too stressed to sleep, ask your GP for some gentle medication to help you relax and sleep. You might not want pills, but what does your body want?
Try to go for a walk every day, don't allow yourself to become a recluse. Concentrate on feeling really well, mentally and physically, this summer.
Try to take a little break away from everything, even if it's just a weekend - on your own. After my husband died I did this a number of times, being away made it easier to listen to myself. I made little plans, and big plans, but always looking forward. Little plans included learning how to fit concealed zips in dresses, bigger plans involved bigger holidays. Now I go to Crete twice a year. Residential care doesn't mean you are no longer a carer, it just changes. Thinking of you today.