Hi Nix and welcome to the forum!
So sorry to read that your both having an awful time lately and do hope matters improve in the New Year. It's early days for your OH and there's a lot to take in when first diagnosed and it all can become overwhelming, hopefully he will find some strength by having you and his sister by his side to guide him through this difficult period in his life.
Some words of advice, make sure you keep in contact with his diabetes team and don't be afraid to ask any questions no matter how trivial they may seem, by keeping a diary of his blood glucose readings and food intake his diabetes team will be able to advise him on adjusting his insulin doses over the coming weeks, if any of his family want to buy him a late Christmas present then I'd highly recommend Think Like a Pancreas by Gary Scheiner.
Diabetes (although not nice and not something you'd wish for on anyone) is a liveable condition and there's no reason why anyone can't lead a full and active life.
Good luck to you both and hope all works out well.