He won't be type 1 diabetic. Type 1 diabetes is caused by an autoimmune disease where the immune system gets bored/over enthusiastic and kills off the insulin producing beta cells in the pancreas.
Surgical removal of the pancreas will cause type 3c diabetes.
There's nothing to suggest that his diabetes will be "brittle", which isn't a medical diagnosis, it's just a descriptor of the diabetes.
Type 3c diabetes is treated similarly to type 1 diabetes with a basal bolus insulin regieme. But you made need to take additional supplements to replace the digestive processes of the pancreas, like creon. Taking creon can make it difficult to deal with high fat food so approach any advice on here to go for a high fat low carb diet with caution. In addition a type 1 diabetic has only lost their beta cells, they still have their alpha cells working fine. It's the job of the alpha cells to react to a hypo by releasing glucagon and telling your liver to release glucose stores. Have surgical removal of the pancreas will mean your husband won't have alpha cells and will need to be more cautious to avoid hypos.
Addisons is an autoimmune disease. Which means it frequently comes along with type 1 diabetes. Getting the right hydrocortisone dose will impact on what the right insulin dose is. Steroids can make you more insulin resistant, but not enough steroid will risk hypos.
To learn about managing diabetes, get hold of the book "think like a pancreas" for a good read of the basics.