I too advise cancelling.
I know it means loosing some money, but honestly will you feel better saving the money and being miserable on holiday?
It is brave of you to try going away on your own, so I would suggest you regard this cancelled holiday as an object lesson in what not to do. It sounds as if it might just be too early for you to revist a place that you and your husband used to go to.
I would suggest you next time book a packet tour making sure there is suitable accomodation and help for you as you have mobility prolems.
Going on a packet tour does not mean you have to go everywhere with the group, as long as you tell the guide that you are not coming, but doing your own thing and when you will be back at the hotel.
Group excursions are not my thing either, but it is, I think, slightly preferable being one of a group and able to get help if needed, than going away alone.